micro chapter 15 unit four

bone marrow

where are blood cells created?

in the bone marrow

Neutrophils and B cells mature in marrow

where do white blood cells mature?

thymus

where do T lymphocytes mature?

bone marrow and thymus

what are the two primary lymphoid organs?

secondary lymphoid organs

where mature WBC’s travel

organs include

• lymph nodes

• spleen

• tonsils

• adenoids

• appendix

• lymph nodes

• spleen

• tonsils

• adenoids

• appendix

what are examples of secondary organs?

specialized, highly specific immune defense that develops after exposure to pathogens, vaccines, or foreign substances

• matures through life

• memory

• specific invaders

• may take a week or more to develop after first exposure

what is adaptive immunity?

Cellular (Cell-mediated) Immunity(adaptive immune response)

—deals with antigens residing within a host cell (virus, intracellular parasite)

Humoral Immunity (adaptive immune response)

—works to eliminate ANTIGENS that are extracellular (bacteria, toxins, viruses in blood)

T- helper cells

act as intermediates between immune cells

T-cytotoxic cells

release cytokines responsible for killing infected cells

T lymphocytes

Cellular immunity is added by…

cellular immunity response

t- helper cells→ activated by macrophage→ TH releases cytokines→ more macrophages

MHC I

surface protein

found on all nucleated cells (every cell EXCEPT RBC)

antigens

Infected cells present foreign molecules

cytokines that direct the infected cell to undergo apoptosis

t cytotoxic cells release…

humoral immune response

characterized by the production of ANTIBODIES that bind to specific ANTIGENS found on the surface of foreign cells

antigen

antigens create antibodies

antibody generator

can induce the production of antibodies against it

epitope

specific region of the antigen at which an antibody binds

Proteins and polysaccharides

induce stronger ANTIGEN responses than lipids and nucleic acids

Antibodies

also called immunoglobulins, are Y-shaped proteins that participate in the Humoral Immune Response

two heavy chains and two light chains

each chain = polypeptide

Antibodies are composed of

Fab region

identical arms of the Y-shape of antibody

Fc region

the stem of antibody

Variable regions

__ is the site at which the antibody binds to an antigen.

This region is unique for each B cell

Constant region

__ determines the biological activity of the antibody. In other words, it determines what happen after the antibody binds to the antigen.

five antibodies

1. IgA

2. IgD

3. IgE

4. IgG

5. IgM

IgA

Secreted into mucus, tears, and saliva, providing mucosal immunity. Also found in breast milk, protecting the intestinal tract of breast-fed infants.

IgD

Found on the surface of dormant B cells. Involved in the initiation of the antibody response.

IgE

Binds at its Fc region to mast cells and basophils, allowing for the detection of parasites and other antigens. Involved in allergic reactions.

IgG

Most abundant class in the blood and tissue fluids. Only antibody capable of crossing the placenta, providing protection to the developing fetus.

Activities include: neutralization, immobilization, agglutination/precipitation, opsonization, complement system activation, and antibody-dependent cellular cytotoxicity.

IgM

__ is a pentamer (5 Y-shaped antibodies joined together at their Fc regions). First antibody produced during primary immune response. Has the same functions as IgG.

Neutralization (antibody function)

a toxin or virus is prevented from interacting with a cell when antibodies coat it

Immobilization (antibody function)

antibodies can prevent movement of a bacteria by binding to the flagella or pili on the cell surface.

Agglutination/Precipitation (antibody function)

bacteria or viruses are clumped together in antibody-antigen complexes

Opsonization

facilitated phagocytosis

organisms that have antibodies bound to their surface are easily recognized and consumed by macrophages

Complement system activation

complement proteins are activated by the presence of antibody-antigen complexes.

Recall that complement stimulates the immune response

Antibody-dependent cellular cytotoxicity (ADCC)

human cells are targeted and destroyed by natural killer cells when antibodies are attached to them.

Antigen Presenting Cell (APC)

surface protein

only cells in the body that express MHC II

macrophage, dendritic cell, B cell

what are the three APCs (antigen presenting cell)

innate immune response

macrophages are activated and begin phagocytizing foreign cells→ cells are digested and antigens are presented on the surface of the macrophage

Plasma Cell

—cell type responsible for manufacturing and secreting antibodies.

Memory B Cell

permanent (long-life) cell that exists for initiating future immune responses against the same antigen

specific T-helper (T_h )

have receptors for the specific antigen

antigens presented by the macrophage activate…

T_h cell

locates a specific B cell that expresses antibody against the presented antigen

B cell is activated through the release of cytokines from the T_h cell.

primary immune response

first time the immune system is exposed to an organism

• —IgM is the first antibody produced

• plasma cells are able to undergo class switching and produce increasing quantities of IgG

• As the infection is resolved, the concentration of IgM returns to zero while IgG remains in small quantities

secondary, or anamnestic immune response

second exposure to the same antigens (on the same strain of organism)

• —Memory B cells respond to second encounter with antigen

• —More cells are available to respond to the antigen

• —Because of class switching, IgG is produced from the beginning of the immune response, and IgG levels are significantly greater than during the primary response.

• —Overall, the response is faster and stronger

T-independent immunity

a branch of the adaptive immune system where B cells produce antibodies against pathogens without requiring help from T cells

• —Simple antigens with repeating epitopes (polysaccharides)

• —Only IgM is secreted (No class switching)

• —No anamnestic response (no “memory”)

• —No processing by antigen presenting cell required

T-dependent

___ immunity is a form of adaptive immune response where B lymphocytes require assistance from helper T cells to produce high-affinity antibodies against antigens, typically proteins.

T-independent antigens

activate B cells without any stimulation from T cells, these are generally polysaccharides

Affinity maturation

—form of natural selection that occurs among proliferating B cells, effectively fine-tuning the ability of the antibody to bind to the antigen.

rate of mutation of antibody genes in very high among activated B cells

autoreactive antibodies (antibodies that attack human cells)

bacterial antigens with similar structure to host antigens

can cause

• Rheumatic Fever following streptococcal infection (strep throat)

• Guillain-Barre syndrome following Campylobacter jejuni infection