4.5 Cell-Mediated Immune Response

1. cell mediated immunity

2. T cells

3. intercellular pathogens

4. directly destroy

what are the steps of the cell-mediated immune response

cell-mediated immunity

driven by T cells, defends against intracellular pathogens by directly attacking infected cells

thymocytes

immature T cells that develop into T cells through positive and negative selection

positive selection

process that exposes T cells to epithelial cells and binds to MHC molecules

fail

T cells that ____ to recognize self-MHC are eliminated via apoptosis

negative selection

self-antigens are presented to peptide-presenting cells of the thymus

bind

T cells that ____ to self-antigens are killed via apoptosis

CD markers

a cluster of differentiation markers found in T cell membrane; the molecular basis of antigen recognition

CD8

a marker that responds to antigens on class I MHC and indicates the cell is infected or abnormal

cytoxic T cells, memory T cells, and regulatory T cells

what are the cells that CD8 markers are found on

cytoxic T cells

fights intracellular infections (virus and cancer) by inducing apoptosis

1. binds to target cell

2. cytotoxic release perforins and granzymes

3. pores are formed

4. granzymes destroy cellular contents

steps of how cytotoxic T cells

perforins

molecules that target the cell membrane and form pores

granzymes

enter cell via pores and degrade cellular contents

cytokines

chemical messengers that activate genes in target cell

memory T cells

await reappearance of the antigen

regulatory T cells

supplies cellular immune response to maintain tolerance

CD4

marker that responds to antigens on class II MHC that indicates the presence of pathogens, toxins, or foreign proteins

helper T cells and memory T cells

what cells are CD4 found on

helper T cells

regulate adaptive immune system through secreting cytokines

Th1

a subtype of helper T cells that regulate the activity of macrophages and T cells

Th2

a subtype of helper T cells that regulate activity of B cells by triggering differentiation into plasma cells

clonal expansion

the process of mitosis of T cells after they become activated and are necessary to make a strong immune response

clonal selection

the process of antigen binding only to those T cells that have receptors specific to that antigen

clone

a group of lymphocytes that share the same antigen receptor and DNA

polyclonal response

the stimulation of multiple types of T cells clones for pathogens with more than one epitope

1. antigen recognition

2. costimulation

3. activation and cell division

how are T cells activated

costimulation

must recieve signal at second site to confirm the first signal; essentially the safety check

memory Th cells

population with extended lifespan ready to expand if antigen returns in the future

tissue typing

determination of MHC molecules in the tissue to be transplanted to better match the donor to the recipient

organ transplantation

replacing failing organs with healthy ones from donors

transplant rejection

recipients immune system identifies transplant as foreign, triggering immune response that attacks and destroys the graft

histocompatibility

property of having the same portion of genes that code for MHC molecules

MHC polygeny and MHC polymorphism

2 characteristics of MHC that make tissue matching more complex

MHC polygeny

multiple MHC proteins on each cell

MHC polymorphism

multiple alleles for each person’s MHC molecules

graft-versus-host dieases

a type of disease from bone marrow transplant that after a failed organ donation it causes donor cells to attack other tissues

rash, and damage to liver and mucosa

what are symptoms of graft-versus host disease

removing mature T cells from bone marrow

how to moderate graft-versus-host disease

immunosuppresive drugs

diminish the strength of body’s immune response to prevent it from attacking a transplanted organ or tissue

3-4 MHC molecules

what is the amount of MHC molecules for a successful transplant