Micro Exam #3

1st line defense

skin, mucous membranes, and antimicrobial substances

2nd line defense

slow or contain infections - inflammation, fever, phagocytes, NK cells

3rd line defense

lymphocytes, memory component

innate (non-specific)

• non-inducible ability to recognize and destroy an individual pathogen or its products

• does not require previous exposure to a pathogen or its products

• external barricades and internal defenses

adaptive (specific)

• acquired ability to recognize and destroy a particular pathogen or its products

• dependent on previous exposure to a pathogen or its products

• directed toward an individual molecular component of a pathogen (antigen)

• takes longer to activate but keeps record

antigen

an individual molecular component of a pathogen (what our antibodies bind to)

natural host defense

the ability of microbes to cause disease Aries between species (ex. HIV can’t be given to dogs)

infection site and tissue specificity

• different pathogens invade different tissues

• route of infection is crucial

Microbiome

• normal microbiota helps host resist pathogens, particularly on the skin and in the gut

• sometimes called probiotics

physical barriers

limits the ability of the microbe to attach or replicate in tissue

(ex. skin, mucous membranes, fluid)

competitive exclusion

• our body’s good bacteria fights for a spot in our body

• typically wins over pathogens which then protects us

chemical barriers

usually destructive to microbes

(ex. sebum, earwax, gastric juice, urine, etc.)

skin

• physical barrier

• 1st line

• epidermis, shedding of top layers

• dry, salty, & acidic plus competitive exclusion

mucous membranes

• physical barrier

• secretion of mucous

• tears and saliva - help dilute and wash away microorganisms before infection can occur

bodily fluids

• physical barrier

• earwax, urine, vomiting, defecation, and diarrhea all help protect our body

sebum

• chemical barrier

• inhibits growth of bacteria, viruses, and fungus via antimicrobial peptides, slightly acidic

• oil

perspiration

• chemical barrier

• helps cool skin and contains lysozyme

lysozyme

• chemical barrier

• enzyme that breaks down peptidoglycan

earwax

• chemical barrier

• physical barrier, but also helps drop pH of the ear canal

saliva

• chemical barrier

• begins to break down starches (amylase)

• has lysozyme, uric acid, and also contains IgA

gastric juice

• chemical barrier

• pH range of 1-3

• found in stomach

urine

• chemical barrier

• contains lysozyme

• is acidic (pH6)

• found in bladder

vaginal secretions

• chemical barrier

• mucus inhibits microbial attachment

• L. acidophilus creates an acidic pH range inhibiting growth

• found in females

probiotics

• lactobacillus, fifidobacterium, and saccharomyces are 3 common ones

• alter pH and oxygen concentrations to inhibit other bacteria

• block pathogenic bacterial effects by producing bactericidal substances

hematopoiesis

production of blood cells and platelets from pluripotent stem cells

neutropenia

low number of immune cells

neutrophilia

high number of immune cells

basophils

• patrol system for foreign bodies

• upon recognizing a microbe, the cell secretes histamine to recruit more immune cells

• histamine causes inflammation

mast cells

• in tissue looking for foreign bodies

• very similar to basophils but do not patrol - stay within tissues (usually CT under the skin & mucous membranes)

• also release histamine and other chemical to induce inflammation

eosinophils

• target parasitic infections and play a role in allergic reactions

• attach to parasites and discharge peroxide ions to destroy then

• seem to be increased in # due to allergies

neutrophils

• most numerous

• 1st to be recruited to site of infection

• phagocytize & destroy bacteria/foreign bodies - use lysosomes

• destroy bacterial toxins in body fluids

• only live a few days

monocytes

• in the blood - macrophages in the tissues

• better at killing variety of pathogens

• live a few months

• present pieces of dead microbes on surface (antigen presentation) and a larger immune response occurs

• present antigens to T-cells

fixed macrophages

residents in tissues and organs

free macrophages

roam tissues and gather at sites of infections

dendritic cells

• phagocytize microbes

• also present pieces of dead microbes on surface to activate adaptive immune response

natural killer cells

• primarily kill virally infected cells, but can help kill cancerous cells and bacteria

• recognize cells that do not display MCH 1

MCH

major histocompatibility complex

granzyme

an enzyme that induces programmed cell death (apoptosis)

perforin

poles holes in (perforates) the target membrane

1 - Recognize the microbe

mast cells and fixed macrophages are the 1st to respond, but eosinophils and basophils are close behind

2 - Recruitment

cells begin to release chemicals (cytokines) to recruit the rest of the immune system via inflammation and fever

3 - phagocytosis

fixed macrophages are 1st but are helped by neutrophils, which are recruited next and are the major phagocytic cells, free macrophages and dendritic cells to eat microbes

4 - induce complement

a cell-free system to kill and target microbes

5 - combating viruses

interferon (a type of cytokine) and dendritic cells

PAMP

• pathogen associated molecular patterns

• structures and molecules not found in or on the host cells

PRR

• pattern recognition receptors

• found on mast cells

diapedesis

release of cytokines and innate cells from blood circulation

pyrogens

fever causing cytokines

transferrins

sequester iron, keeping it away from pathogens and limiting their growth

chemotaxis

chemical signals attract phagocytes to microorganisms

adherence

attachment of a phagocyte to the surface of the microorganism

MAC

• membrane attack complex

• poke holes in the cell

opsonization

help phagocyte grab microbe

interferons

• small cytokine proteins that are produced by virally infected cells

• serve as a warning system

• prevent viral replication by stimulating the production of antiviral proteins

humoral

• B cells

• antibodies from those B cells recognize antigens of non-self cells and mark them for destruction

• mostly fight invaders outside of the cell

cellular

• T cells

• primarily respond to antigens after they have made their way inside a cell

• involved in cytokine production attacking infections and memory cells

B cells

• originate and mature in bone marrow

• mature into plasma cells or memory cells

plasma cells

• fight infection by producing antibodies which attach to bacteria or viruses

• agglutination, enhances phagocytosis, activation of complement, neutralization

memory cells

• live a long time

• can differentiate into plasma cells during a subsequent infection

T cells

• originate in bone marrow and mature in thymus

• 98% killed in the thymus (not smart enough)

• all mature by the time you reach puberty

helper T cells

• CD4

• release cytokines and call in reinforcements

• once activated - produces more helper T cells, memory T cells, cytotoxic T cells and regulatory T cells

cytotoxic T cells

• directly kill bacteria or infected host cell

• use granzymes and perforin

• looks for antigen presented on MHC 1 on infected host cell

regulatory/suppressor T cells

• stops immune response

• also inhibit food allergies

memory T cells

• long lived and help speed up the process during subsequent infection

leukocytes

all WBCs - mast cells, basophils, eosinophils, etc.

lymphocytes

• immune cells often found in lymph nodes

• primarily B & T cells, also can include NK cells

1 - antigen presentation

innate immune cells must present a piece of the microbe to T cells

2 - clonal selection and expansion

only B & T cells that recognize the antigen begin to grow

3 - release of cytokines

many different cytokines are released to induce a robust immune response

4 - killing virally infected cells

T killer cells are primed by T-helper cells and kill virally infected cells

5 - antibody release

antibodies neutralize and help with opsonization of microbes and toxins

6 - memory

memory B & T cells remember the microbe in case the host is infected again

antigen presenting cells (APCs)

• engulf, process, and present antigens to lymphocytes

• macrophages, dendritic cells, and B cells

antigen

• protein or polysaccharide that stimulates immune system

• substance that reacts with antibody molecules and antigen receptors on lymphocytes

epitopes

the actual proteins or fragments of an antigen that react with receptors (5-15 amino acids or 3-4 sugars)

MHC 1

• on all nucleated cells

• signals “we need help” or “i’m infected”

• CD8+ or T cells

MHC 2

• only certain immune cells

• Signals “we need help”

• CD4+ T cells

interleukins

cytokines which serve as the intermediary between leukocytes

chemokine

cytokines that induce migration of leukocytes into areas of infection

interferons

originally named for interfering with viral infections

tumor necrosis factor

cytokines named because originally seemed tumor cells were targets - involved in inflammation

hemopoietic cytokines

these aid in the control of the pathway of WBC recruitment and maturation

cytokine storm

cytokines also stimulate the production of more/other cytokines - these loops can get supercharged and can cause overproduction

IgA

• found in mucous, saliva, tears, and breast milk

• prevent adherence of microbes to mucosal surfaces

• short-lived

IgD

• part of the B cell receptor

• activates basophils and mast cells

IgG

• secreted by plasma cells in the blood

• able to cross the placenta into the fetus

• most abundant and long-lived

IgE

• protects against parasitic worms

• responsible for allergic reactions

IgM

• may be attached to the surface of a B cell or secreted into blood

• responsible for early stages of immunity

• short-lived

hypersensitivity

inappropriate immune response that results in host damage

Type 1 Hypersensitivity

• caused by IgE antibodies

• reactions occur within minutes after exposure

• often though of as an allergy

Type 2 & 3 Hypersensitivity

• typically a result of IgG antibodies

• occur within 24 hour of exposure

type 2

Rh factor rejection in mother of a Rh+ child

type 3

rheumatoid arthritis

type 4 hypersensitivity

• result of T killer cells attack the host or T helper cells

• immune system has mistakenly decided that a host protein is a foreign antigen

SCID

• severe combined immune deficiency syndrome

• serious, congenital deficiency of both B and T cells

AIDS

• acquired immunodeficiency syndrome

• caused by HIV infection that progresses and kills CD4 and T cells

immunity

the ability of an organism to resist infection

active natural

exposed to the disease

passive natural

antibodies cross placenta or breast milk (temporary)

artificial active

active immune system responses to antigen from vaccine