Parasitology Final

The study of the most common mode of life on earth

• Centered on animal parasites of humans, domestic animals and wildlife

An organism that lives in or on another organism (host) and can either harm or live off the host at the host’s expense

1. Parasite resistance

2. Insecticide resistance

3. Increased Mobility (popularity in tropics and subtropics)

4. Migration of refugees from war-torn areas

5. Military service personnel coming home from abroad

6. Modifications of the environment

7. Climate change (disease causing parasites spread from tropics and more temperate regions)

8. Immunosuppression becoming more widespread:

9. AIDS; Cancer chemotherapy; and organ transplantation

10. Indiscriminate release of toxic chemicals and carcinogens into the environment

•  place eggs in other compatible bird’s nest when the parent birds are away

•  is a parasitic fish that attaches to fish urethra because they are attracted to urrea and feed off of the host fish blood. There Have been instances of them latching onto human ureters.

Likes Stagnant Water

Is the host

Competes with Esculentus without passing genes

Likes moving water

Is the parasite

Passes genes to Esculentus

Can live in both moving and stagnant water

Encroaches on lessone and does not transfer their genes

Quant person who seeks truth in strange places

Interactions among organisms in which one organism lives with, in or on the body of another

Organisms involved in symbiotic relationships with other organisms, the host

Is a lack of benefit or detriment experienced by either members of the pair of interacting organisms.

• It describes interactions where the fitness of one species has absolutely no effect whatsoever on that of the other.

Some degree of overlap in ecological niches of two populations in the same community, such that both depend on the same food source, shelter, or other resources, and negatively affect each other’s survival

• Carnivorous animals compete for prey

• Plants compete for sunlight, water, nutrients, pollinators, and dispersers of fruits and seeds

• The bladderwort plant (Utricularia) competes with tiny fishes for small arthropods.

Form of symbiosis when the symbiont (phoront) is mechanically carried about its host: neither is physiologically dependent on the others

• Means “to carry”

• Ex. Bacteria on legs of a fly

• Ex. Fungal spores on feet of a beetle

• Aquatic snail eggs laid on birds feet

• Dermatobia hominis (Human botfly)

A mutually beneficial symbiosis between organisms in which the interaction is NOT physiologically necessary to the survival of either

• Egyptian plover eats residuals from crocodile teeth

• Cattle egret remove ectoparasites from the back of antelope & Cow

• Hermit crab shell covered with sea anemones

• Ant and aphids with honeydew

Type of symbiosis In which both host and symbiont benefit from association

• Usually Obligatory

• In most case there is physiological dependence

• Must Know

1. Termites and intestinal protozoan fauna 

2. Blood-sucking leeches and intestinal bacteria

3. Cleaning symbiosis: Cleaner Wrasse (Labroides Dimidiatus)

4. Lichen: Microscopic green algae or cyanobacteria and filamentous fungi

A kind of symbiosis in which the symbiont (a commensal) benefits, and the host is neither harmed nor helped by the association

• Means “Eating at the same table”

1. Pilot fish and remoras

2. Barnacle on a whale

3. Epiphytes on a tree

4. Entamoeba gingivalis

Asymmetrical interaction in which one organism causes a negative effect on another without being positively or negatively affected in return

• Bread mold Penicillium that produces penicillin, an antibiotic that kills bacteria

• Black walnut tree (Juglans nigra) produces juglone, an organic compound that is toxic or growth-stunting to many types of plants.

Animal interaction in which a predator kills its prey outright; it does not subsist on the prey while the prey is alive

A symbiosis in which a symbioint benefits from the association, while it harms the host in some way or lives at the expense of the host

Large parasites that do NOT multiply in the host of interest

• Do NOT induce lasting immunity (some exceptions)

• Have more stable populations, and cause endemic diseases

1. Helminthes, arthropods, and other metazoans

Small (or very small) parasite that multiplies within the host of interest

• Induce lasting immunity

• Have unstable populations, and cause epidemic diseases

1. Fungi, protists, bacteria, and virus

Parasites that live on the outer surface of its host

Parasite that lies in the host

They cannot complete their life cycle without spending at least part of the time in a parasitic relationship

Not normally parasitic but can become so when they are accidentally eaten or enter a wound or other body orifices

A parasite found in host other than its normal host

• Puts host and parasite into environmental conditions to which neither is well adapted

A parasite that lives its entire adult life within or on a host

A parasite that contacts its host only if you feed and then leave

Organism that is a typical parasite early in its development, but finally kills its host during or at the completion of its early development

• Often used in reference to many insect parasites of other insects

• Approximately 10% of described insect species are parasitoids.

Condition in which an organism is a parasite of another parasite

A parasite living in the lumen of a hollow organ

A parasite living within the tissues of a host

A any agent, such as water, wind or insect (host), that transmits a disease organism

Host in which a parasite achieves sexual maturity; if there is no sexual reproduction in the life of the parasite. This is the most important host

Host where the parasite develops some but fully to sexual maturity

Host in which a parasite survives without undergoing further development

Serves as a means of sustaining a parasite when it is not infecting humans, which is usually also another definitive host

• Normal to human environment

• Involves domesticated animals

• Existing normally in the wild

• Involves wildlife

Any group of individuals, usually of a single species, occupying a given area at the same time

A permanent change in a cell’s DNA and includes: changes in nucleotide sequences, alternation of gene position, gene loss, or duplication, and insertion of foreign sequences

A relative reproductive success (relative fitness) of an allele or genetype as compared to other alleles or genotypes

The possession of a trait that coincidentally predisposes an organism for survival in an environment different from those encountered in its evolutionary history; may occur because a natural population carries a huge quantity of genetic variability

• Dinosaurs feathers initially used for insulation and display

• Origin of larynx initially helped air-breathing fish gulp air

An evolutionary process whereby a population becomes better suited to its habitat over many generations

• An anatomical structure, a physiological process, or behavioral trait that promotes the likelihood of an organism’s survival and reproduction in a particular environment.

• Adaptation of parasites to host internal environments.

A composite of all the forces that cause differential survival and differential reproduction among genetic variants (artificial selection vs. Natural selection); a key mechanism of evolution

• Reciprocal selection pressures exists between parasites and their hosts

Genetic changes in populations of organisms through time that leads to differences among them

• Evolution only occur when there is a change in gene frequency within a population over time

• These genetic differences are heritable and can be passed onto the next generation.

1. Encounter the host

• Parasites that possess a genetically determined behavioral trait that increases the probability of encountering the host

2. Allow the parasite to live in the host

1. Avoid encountering the parasite

2. To get rid of the parasite if encounter has taken place

Originally proposed by Leigh Van Valen (1973)

• Metaphor of alice and the Red Queen

• Species have to “run” (evolve) in order to stay in the same place (extant)

• Cessation of change may result in extinction

Ex. Parasite-Host Coevolution

• Each time the parasite population acquires a new “weapon”, the host population is led to produce a new defense.

• Parasite and host populations are engaged in an “endless” arms race/ war

Produces more eggs and sperms than their free-living relatives do

• Higher reproductive potential

• Asexual reproduction

• Hermaphroditism

• Self-Fertilization

1. Adaptive advantage of parasite behavior

2. Parasite may alter host behavior

1. Size- Many parasites are larger than their free-living relatives

2. Attachment organs- Suckers, hooks & spines, penetration organs, and cysts, etc

3. Loss (regression) of anatomical Structure- Organs of sense, locomotion, digestion, etc

1. Energy Metabolism - Catabolic pathways are usually reduced or modified in many parasites

2. Nutrient Uptake- There is an elaboration of a transport mechanism for acquiring monomers / Ex. Glucose, amino acids, etc

3. Synthetic reactions- Synthetic capacities of parasites are reduced when compared with their free-living relatives.

1. Absorption of host antigen

2. Antigenic variation

3. Occupation of immunologically privileged sites

4. Disruption of the host’s immune response

5. Molecular mimicry

6. Loss of masking of surface antigens

1. Reduction in the extent of the free-living phase of the life cycle

2. Behavioral responses to locate favorable environments

3. Responding to chemical stimuli from their host

4. Changing the behavior of the infected intermediate host to increase the chances of them being eaten by the final host

5. Infection of secondary and tertiary hosts (why??)

1. Increased reproductive potential, since asexual reproduction can take place in the intermediate host

2. Increase the range of the parasite in space and time

3. By infecting more than one host species the parasite can survive when one host is scarce

4. An intermediate host can channel to a definitive host if not enough.

Studies performed that are non-hypothesis driven;

• Includes the discovery of: New Parasites

• Parasite morphology

• Life Cycle trends

• Population survey of infected or non infected hosts

• Proper identification of parasites and host is essential in trying to control diseases

• It is Naive to try to control an infection without knowledge of how the parasite reproduces and gets from one host to another.

A system in which a species is given a compound name

• Carolus Linnaeus (1701-1778), father of modern taxonomy

• 1st word is the genus in which the species is placed (first letter capitalized)

• 2nd word is the species epithet (uncapitalized) used to separate a species from other members of the same genus

• Named of genera and lower taxa are always 

Study of scientific classifications; ordering & naming organisms

• Basic sub discipline of biology

• Scientific name carries with it massive amounts of information

• Includes (1) through (4)

1. Describe organism in detail

2. Provide scientific names for new species

3. Preserve collections (permanent slides and voucher specimens)

4. Classification of the organism, keys for their identification, and data on their distributions

5. Investigates their evolutionary histories

6. Considers their environmental adaptations

Study of classification & biological diversity within an evolutionary context

• Seek to understand the origin of diversity at all levels of classification

• Includes (1) through (6)

1. Describe organisms in detail.

2. Provide scientific names for new species

3. Preserve collections (permanent slides and voucher specimens)

4. Classification of the organism, keys for their identification, and data on their distributions

5. Investigates their evolutionary histories

6. Considers their environmental adaptations

Is a Methodology used by systematists to infer (hypothesize) a species evolutionary history (phylogeny)

• Pioneered by Willi Hennig (1913-1976)

• Used in the discovery of monophyletic groups (evolutionarily real entities)

• This method relies on shared derived character states (Homology)

1. Change in characteristics occur in lineages or groups over time.

• Only when characteristics change are we able to recognize different lineages

2. Any group of organisms are related by descent from a common ancestor.

• Supported by many lines of evidence

3. There is a bifurcating or branching pattern of cladogenesis.

• When a lineage splits, it divides into two exactly groups

Evolutionary hypothesis of the origin and diversification of a taxon

• Treelike diagram

• Relationships between taxa are shown in the branching patterns

• Characters among the taxa used to produce phylogenies include: (anatomical, behavioral, physiological, or molecular attributes)

1. A group of organisms that includes an ancestor and all descendants of that ancestor

2.  A taxon of Interest

3. A related taxon for the purpose of comparison, more basal

4.  Internal branch point that represents the common ancestor of those descendents; a speciation event

5. Two descendents that split from the same node

1. A character is similar in two taxa because their common ancestor had that character

2. A similar character that has the same function but different evolutionary origin

Is similarity NOT due to homology; resulting from convergence, parallelism or reversal

Ancestral Characters; present in both the ingroup and outgroup

• Uninformative Character

Derived Character, evolutionary novelty; present only in one taxon of the ingroup

• Uninformative Character

Shared derived characters that set a taxon apart from related taxa and their most recent common ancestor

• Informative character

1.  A group of taxa that includes a hypothetical ancestral taxon and all its descendants

• Defined by a suite of shared-derived characters (Synapomorphies)

2.  A group of taxa that includes a hypothetical ancestor but does not include all of the ancestor’s descendants

• Defined  by a suite of ancestral traits

 3. A group of taxa that do not share a most recent common ancestor

• Defined by convergent traits (homoplasies)

A functional system who components attack foreign substances or prevent their entry into the body

Stat in which a host is more or less resistant to an infective agent

• Used in reference to resistance arising from tissues that are capable of recognizing and protecting the animal against nonself invaders

A mechanism of defense that does not depend on prior exposure to the invader

A mechanism of defense that is specific to the particular nonself material: requires time fore development, and occurs more quickly and vigorously on secondary response

1.  as an effective barrier against pathogens

• Oil & Sweat glands give skin surface pH of 4-5.5

• Sweat conations lysozyme (Digest bacterial cell wall)

• Normal Flora include non-pathogenic bacteria & fungi

• Epidermis 10-30 cells thick, dermis 15-40 times thicker

1. an an effective barrier against pathogens

A.) Digestive Tract

• Saliva Contains lysozyme (also in tears)

• Acidic environment of stomach pH 1.5-3.5 (Concentrated HCl solution)

• Digestive enzymes in intestine

• Nonpathogenic normal flora

• Vomiting & diarrhea may expel pathogens

B.) Respiratory tract

• Pathogens trapped by mucus in bronchi and bronchioles

• Ciliated epithelial cells sweep mucus toward the glottis

• Coughing and sneezing expels pathogens

C.) Urogenital tract

• Viginal secretion viscous and acidic

• Secretions promote growth of normal flora

• Acidic urine of both sexes may wash out pathogens

• Recognizes a wide spectrum of pathogens without a need for prior exposure

• Key players include neutrophils, monocytes, and macrophages

• These cells phagocytose pathogens and trigger the cytokine and chemokine network

• can lead to inflammation and specific immune response

• Except for Erythrocytes (Which are red cells) the rest are white cells.

A.) Macrophages

1. Monocytes mature into active macrophages at site of infection

2. Intracellular killing and digest pathogens via phagocytosis

3. Phagosome fuses lysosome, (oxygen-containing and nitrogen-containing free radicals)

4. Roam continuously in the extracellular fluid bathing tissues

5. Antigen-presenting cell (APC) for helper T cells (TH)

6. Respiratory burst for additional cell-killing ability (liberates deluge of free radicals

7. Express Fc receptor molecules for IgG to trap antigen-antibody complexes

A.) Neutrophils

1. Most abundent circulation leukocytes (50-70% of peripheral blood leukocytes)

2. Frst cell on site of tissue damage or infection

3. Intracellular killing via phagocytosis, greater range of reactive oxygen radicals

4. Large numbers in blood until attracted to tissues during inflammation

5. Roam in the extracellular fluid bathing tissue

B.) Eosinophils

1. 2%-5% of total leukocytes in blood 

2. Important in the elimination of parasites

3. Degranulation, next to parasite, releases extremely potent mediators (enzymes & toxins)

4. High blood count is often associated with parasitic infection & allergic diseases

5. Express Fc receptor molecules for IgE

C.) Basophils

1. Ciculating cells, least numerous at about .5%

2. Not important as phagocytes

3. Release mediators such as histamine to promote inflammation

4. Express Fc receptor molecules for IgE

Natural Killers (NK) Cells

1. Do not kill pathogen directly, but induce apoptosis of infected cells (Cancer and Viral)

2. Release perforins, insert in membrane and make pores, granzymes enter infected cell and activate capase enzymes that induce apoptosis

3. Big player in immune surveillance and the bodies defense against cancer

4. Do not have T-cell receptors, but do express Fc receptor for IgE

1. Primarily located under mucosal surfaces

2. Release chemical mediators such as histamine to promote inflammation

3. Triggered during allergic responses

4. Express Fc receptor molecules for IgE

5. Important component of the inflammatory response

Occurs over seconds, minutes, hours and days

• Chemical Signals are released by infected or injured cells during inital response to tissue damage (acute phase).

1. Dilation of local blood vessels increases blood flow at site (red & warm)

2. Increase permeability of capillaries causing edema (tissue swelling)

3. Tissue swelling puts pressure on nerve endings (pain & potential loss of function)

4. Macrophages and neutrophils release cytokines interleukin-1 (IL-1) and tumor necrosis factor (TNF) which acts on hypothalamus to raise body temp. (fever)

1. Fever is one of the most common symptoms of infection

2. Fever stimulates phagocytosis and causes liver and spleen to store iron and zinc needed by bacteria

3. Fever may destabilize certain viruses and bacteria

       5.)  Cell death (necrosis) always occurs to some degree during inflammation

 A type of ANTIBODY-MEDIATED immunity which involves degranulation of basophils and mast cells in the area

1. Basophils and mast cells have receptors that bind the Fc portions of antibody (IgE)

2. When exposed to the same allergen a 2nd time, degranulation occurs

3. Results in dilation of local blood vessels and increased permeability; edema

4. Immediate hypersensitivity is important in some parasitic infections

5. Immediate hypersensitivity in humans is the bases of allergies and asthma

hypersensitivity produced by exposure to further doses of the same protein, usually when exposure is within less than 2 weeks

• Basophils and mast cells release pharmacologically active substances

• Widespread rapid inflammatory responses that may be fatal f not treated rapidly

• Tremendous drop in blood pressure.

Acute inflammation that fails to heal; occurs over longer times and is disease related

• Fibrosis: arise from abnormal and continuous wound repair processes that fails to terminate resulting in elevated levels of collagen and scarring

• Granulomas: Nodules of inflammatory tissue that may accumulate around persistent antigen

• Abscess: When necrotic debris confined to a localized area forms pus that may cause an increase in hydro-static pressure

• Ulcers: An area of inflammation that opens out to a skin or mucous surface

A. Complement

1. Consists of approx. 30 different proteins

2. Circulate freely in blood plasma, generally in inactive form (Zymogen)

3. Complement can be activated by classical pathway (antigen-antibody complex) or alternative  pathway (spontaneously) or lectin pathway (cell wall polysaccharides of certain bacteria and fungi)

4. Complement proteins (C3b) coat pathogen surface (opsonization), thus promoting phagocytosis and destruction of pathogen by macrophages and neutrophils which have receptors for C3b

5. C5a is an important chemotactic protein, helping recruit inflammatory cells

6. Complements C5b initiates pathway for membrane attack complex

B. Intererons (IFN-A, IFN-B, IFN-y)

1. A class of proteins synthesized upon parasitic infection of a cell

2. Acts as messengers to protect normal cells in vicinity from becoming infected

3. IFN-A and IFN-B include the degradation of RNA and block protein production 

4. IFN-y is produced by TH cells and natural killer cells to stimulate cells in the cellular response

A. Cytokines

1. Cytokines are protein hormones utilized by immune cells to communicate 

2. Can effect same cells that produce them, cell nearby, or cells distant in the body

   B. Cell signaling

1. Ligand binds to a specific cell receptor protein initiating intracellular signal cascades

2. Ligands may be located on cell surface of neighboring cells, dissolved in blood (Cytokines) or on the surface of or secreted by pathogens

3. Cascades may activate transcription factors or proteins that control gene induction, cell death, and secretion

JACK-STAT pathway: 3 main components include:

1. Receptor

2. Janus Kinase (JAK)

3. Signal Transducer and Activator of Transcription (STAT)

• Transmembrane receptor, activated by cytokine

• Activates the JAK protein, which adds phosphate groups (P) to the receptor

• Kinases: Proteins that add phosphate groups to othe proteins

• Phosphate groups: act as an “on” and “off” switch on proteins

• STAT is recruited and itself becomes phosphorylated forms dimer, and moves into the cell nucleus, where it binds to DNA promoter region.

Receptors with broad specificity that bind to molecules on the surface of pathogens; stimulated by PAMPs

• Pathogen-Associated molecular patterns (PAMP): A small molecular motifs conserved within a class of pathogens

1. Scavenger Receptors: Bind lipoproteins and lipopolysaccharides from bacterial cells including Gram-Positive

2. Complement Receptors: Integral membrane proteins that recognize fragments of complement and mediate various defense functions, including phagocytosis

3. Toll-Like Receptors (TLRs): Single, membrane-spanning, receptors that recognize structurally conserved molecules of carbohydrates, nucleotides, and proteins derived from viruses, bacteria, protozoa, and helminthes parasites.

1. Nonself recognition:ability to distinguish self-antigens from nonself 

2. Anti-gen Specific: Recognizes and is directed against specific antigens

3. Systemic Response: Immunity is not restricted to initial infection site

4. Memory: Recognizes and mounts stronger attack on previously encountered pathogens

Major Histocompatibility Complex (MHC): Cell surface glycoproteins, highly polymorphic

1. MHC Class I Proteins

• Present on every nucleated cell of the body (few exceptions)

• Cytotoxic T cells (CD8) respond to endogenous antigen bound to MHC Class I proteins

2. MHC Class II Proteins

• Found only on antigen presenting cells (macrophages, B cells, and dendritic cells)

• TH cells (CD4) respond to exogenous antigen bound to MHC Class II proteins

1. Cell-mediated Immunity: Entirely associated with cell surfaces, T-cell receptors, that are unable to “see” free antigens

T Cells: Can regulate the immune responses of other cells (CD4) or indirectly kill cells (CD8) that carry specific antigens

1. Lymphocytes produced in red bone marrow, migrate to thymus (primarly lymphoid organ) where they mature (VDJ recombination of T cell receptors) and undergo selection

2. T-cell receptors must recognize self MHC proteins needed for activation, but not the self antigens (self tolerance) that the MHC presents (T-cell eliminated in thymus if criteria not met)

3. “Naive” T cells recirculate only between blood and lymphoid organ (Ex. Spleen, tonsils, or lymph nodes)

4. T-cell receptors re transmembrane proteins with constant and variable region, like antibodies:; composed of 2 chains (alpha and beta)

5. T-Cell receptors recognize only a processed peptide fragment that the APC’s MHC presents to the T-cell receptor, unlike B-cell receptors

6. Other transmembrane proteins closely linked to T-cell receptors serve as coreceptors, such as CD4 and CD8

7. T Cell activation occurs in secondary lymphoid tissue when antigen is displayed with self MHC on mature dendritics cells (DCs)

Kill cells that are infected with viruses (or other pathogens)

1. Have CD8 coreceptor protein

2. Antigen-presenting cell (APC) often include dendritic cells (professional APC)

3. Activated by endogenous antigens bound to MHC class I proteins of dendritic cells

4. Activation results in the release of IL-2, TNF, and IFN-y; and they differentiate into memory cells and activated cells (clonal expansion)

5. “altered -self” cells expressing the same combination of foreign peptide on MHC cless I are targeted; may include tumor cells, virally infected cells, or cells with intracellular parasites

6. Relase perforins, insert in membrean and make pores, granzymes enter infected cell and activate caspase enzymes that induce apoptosis

Involved in activating and directing other immune cells; their cytokines larger determine whether an immune response is humoral or cell-mediated; not killing ability

1. Have CD4 corecpetor protein

2. 1st signal is initiated by exogenous antigens bound to MHC class II proteins of macrophages, dendritic cells (phagocytosis or endocytosis), and B cells (receptor-mediated endocytosis)

3. 2nd signal is a verification step, naive TH cells express the protein CD28 that must bind to costimulatory B7 protein on professional level

4. When 2nd activation signal is complete the originally undetermined T-Helper null cell (TH0) releases a potent T cell growth factor celled interleuin 2 (IL-2) which activates the T-cell’s proliferation pathways

5. TH0 cells differentiate into TH1 or TH2 cells depending cytokine environment Cellular Response- IL-12 & IFN-y induces TH1 differentiation; IFN-y inhibits TH2 cells Humoral Rsponses- IL-4 drives TH2 differentiation, and inhibits TH1 cell production

6. Both T helper cells group are able to inhibit the activation of the other group using their own cytokines

• TH1 Cells communicate attack against intracellular bacteria and protoza

• TH2 cells communicate attack against extracellular parasites including helminths

• TH1 Cells mainly secrete

• IL-2

• IFN-y

• TNF

• GM-CSF

• TH2 Cells mainly secrete

• IL-4

• IL-5

• IL-10

Based on antibodies on cell surfaces and in body fluids (blood, lymph, etc)

Bind specific to free (soluble) antigen or particulate antigen with its membrane bound antibody (B cell receptors); also serves as APC to TH cells

1. B cells produce in red bone marrow; immunoglobulin (Ig) synthesis occurs

2. Ig is encoded by different segments of DNA, a V (vaiable) segment, a D (diveristy) segment, a J (joining) segment, and a constant region; variable regions are shuffled by RAGs

3. Each Ig consists of 2 identical short polypeptides called light chains and 2 identical longer polypeptides chains called heavy chains; held together by disulfide bonds to form a Y-shaped molecule

4. Each “arm” is called FAB (fragment antigen-binding) region and the “stem” is called Fc (Fragment crystalization)

5. Immunoglobins IgM (monomeric form) and IgD are present on mature “naive” B cells

6. B cell recirculate only between blood and lymphoid organs, activated in secondary lymphiod organ

7. B cells recognize their cognate antigen in its native form with its B-cell receptors (atibodies); each Ig can bind 2 identical epitopes

8. Binding of antigen to Ig on surface o appropriate B cell is usually not sufficient to activate the B cell to multiply; so, B cell (APC) internaizes antigen-antibody complex and incorporates portions of antigen (epitope) on MHC II

9. Specific TH2 Cells recognizes antigen displayed by B cell; cytokinesis

1. Plasma B-cells: Are large B cells that have been exposed to antigen

• Produce and secrete large amounts of antibodies

• Short lived die after threat is eliminated

2. Memory B cells: Specific to antigen encountered during primary immune response

• Can espond quickly should the threat re-appear

• Long lived cells

Each B cell can only produce antibodies attacking a specific antigen.

IGM: Pentamer, 1st antibody secreted during primary immune response; monomer, present on surface of B cells

IgG: Monomer, major antibody secreted during the secondary response; 75% of plasma antibodies

IgD: Monomer, present only on surface of B cells; serves as antigen receptor

IgA: Dimer, most abundant form of antibody in body secretions; high density of IgA-secreting plasma cells in MALT

IgE: Fc binds to mast cells, basophils, etc; often secreted in response to helith worms

A retrovirus that attacks the body’s immune system; caused by AIDS

1. HIV mounts direct attack on TH cells and binding to CD4 proteins on cell surface; monocytes are infected

Phylum containing simplest bilaterally symmetrical animals

• Most are parasitic

• Acoelomate body plan (No body cavity other than the gut); rarely has anus

• Tripoblastic (Composed of three fundamental cell layers)

• Doroventrally flattened (greater surface area to respire by diffusion)

• Tegument (surficial covering of a multicellular organism, an intergument)

• Parrnchyma (Loosely arranged mass of fibers and cells of several types)

A subclass within the class trematoda

Most are dorsoventrally flattened and oval in shape; others as thick as they are wide

• Length ranges from 1.0mm to 6.0cm

1. Oral Sucker: Muscular sucker that surrounds the mouth

2. Acetubulum: Ventral sucker of a fluke

3. Distome: Fluke with two suckers, oral and ventral

4. Monostome: Fluke that lacks a ventral sucker

5. Amphistome: Fluke with the ventral sucker located at the posterior end

Surficial covering of a multicellular organism, an integument

• Distal Cystoplasm: Anucleate layer of cytoplasm above a”Sunken epidermis”

• Cytons: Cell bodies containing nuclei; lie below the superficial muscle layers

• Internuncial processes: channels that connect cytons to distal cytoplasm

• Syncytial: Describes the continuous distal cytoplasm with no intervening cell membranes

• Spines: Consist of crystalline actin; often present in certain areas of the tegument

  1. Spines lie above the basement membrane of the tegument