adaptive immunity T; cells

what is cell-mediated immunity

Immune response that does not involve antibodies

what does cell-mediated immunity do

involves the activation of phagocytes, antigen- specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen

what does the whole T cell react directly in contact with

target cells

what do T cells also stimulate 

other T cells, B cells and phagocytes 

antigen

a toxin or other foreign substance

what do antigens induce

an immune response, especially antibody production

what do antigens have

epitopes (antigenic determinants)

what part of the antigen is recognized by the immune system

epitope

MHC I has a unique

characteristic of self

what does MHC ll have

immune regulatory receptors

Cells that express MHC II are

antigen presenting cells (APCs)

“Professional” APCs possess

both MHC molecules

“Professional” APCs possess

Macrophages, Dendritic cells, B cells

why do APC’s process antigens

so it is recognizable by T cells

where are MHC 1 found on

most cells

what type of antigens are MHC 1

endogenous

in MHC 1 Ag’s (antigens) are processed in

cytoplasm

in MHC 1 Ag’s (antigens) are recognized by 

CD8 T cells 

where are MCHll found 

only on APC’s 

what type of antigens are MHCll

exogenous

where are antigens processed in MHC ll

endosomes

what are antigens recognized by in MHC ll

CD4 T Cells

T-cell receptor (TCR) role 

recognizes antigen 

CD4 or CD8 (on T cells)

recognize MHC

CD4 recognizes

Class II MHC (on APC)

CD8 recognizes

Class I MHC (on most cells)

CD3 complex is the

activation “switch”

accessory molecules for T cells

second signal and attachment

what are cytokine receptors needed for

further signaling

where does T cell development occur in

the thymus 

in T- cell development TCR genes are

rearranged

in T cell development self- reactive cells are

destroyed

in T- cell development surviving cells mature into

– helper T cells (CD4)

– cytotoxic T cells (CD8)

– gamma/delta T cells

T-cells recognize antigen only when it has been

processed and presented by a cell with MHC

• usually macrophage or dendritic cells 

After interaction with antigen/MHC, T cells

divide into one of many effector cells

what do T helper cells express

CD4

what is the most prevalent type of T cell in blood and lymphoid organs

T helper cells

what do T helper cells activate

specific immune responses

• B cells, T cells

what else do helper T cells do

Activate macrophages & increase phagocytosis

what do helper T cells release

lL-2 IL-4, -5, -6

lL-2 release…

stimulate groeth of B and T cells

what does IL-4, -5, -6 do

stimulate various B cell activities

what are T helper cells activated by

MHC ll/ antigen

after T helper cells are activated by MHC ll/ antigen the t helper cells 

Differentiate into T helper 1 (TH1) or T helper 2 (TH2)

T cell helper 1 (TH1) express 

CD4

T cell helper 1 (TH1) activated by 

MHC II/antigen

T cell helper 1 (TH1) activates

other CD4 and CD8 cells

T cell helper 1 (TH1) secretes

IL-2, tumor necrosis factor (TNF), and interferon gamma (cytokines

T cell helper 2 (TH2) expresses 

CD4

what does T cell helper 2 (TH2) drive

B- cell proliferation

what does T cell helper 2 (TH2) secrete 

IL-4, IL-5, IL-6, IL-10 (cytokines)

what can T cell helper 2 (TH2) dampen

TH1 activity

what does T regulatory cell (Treg) express 

CD4, CD25

what is T regulatory cell (Treg) involved in 

– development of immune tolerance

– suppression of pathological immune responses

– Inflammation

– autoimmunity

what does T cytotoxic cell (TC) express

CD8

what does T cytotoxic cell (TC) destroy

a target foreign cell by lysis

what are T cytotoxic cells (Tc) important in

– destruction of cancer cells

– virus-infected cells

– graft rejection 

what do T cytotoxic cell (TC) require to function

MHC l

T cells with CD8 receptor recognize

peptides presented one MHC l

Cytotoxicity

capacity of certain T cells to kill a specific target cell

T cytotoxic cell (TC): killer T cells injures target cells by release of 

granzymes and perforins 

Granzymes

enzymes digest proteins

perforins

proteins that punch holes in membranes of cell

release of granzymes and perforins leads to

programmed cell death = apoptosis

superantigens structure

spans MHC-II and TCR on cells

superantigens

Class of antigens that cause non-specific activation of T-cells

superantigens results in

polyclonal T cell activation and massive cytokine release

what do superantigens promote

overwhelming immune responses

where are super antigens found

primarily in bacteria and viruses

superantigens are a form of

virulence factors

what to superantigens cytokines release

– tumor necrosis factor

– interleukins-1 and -6

superantigens Massive influx of such potent mediators leads to

– blood vessel damage

– toxic shock

– multiorgan failure