36 - Adaptive Immunity Pt 2 (T-Cells)

Cell-Mediated Immunity

Immune response that does not involve antibodies that instead involves activation of phagocytes, antigen specific cytotoxic t-cells and release of cytokines

The Whole T Cell Reacts

Directly in contact with target cells (and not by secretion of molecules into circulation like B cells)

T Cells Stimulate

Other T Cells, B Cells, and Phagocytes

MHC I

Presents self antigens/things from the host cell, endogenous antigens

MHC II

Immunoregulatory receptors that present foreign antigens (APCs), exogenous antigens

APCs Composition

Macrophages, Dendritic Cells, B Cells

What is the purpose of APCs processing antigens?

So that the antigen is recognizable by T-Cells

Endogenous Antigens

MHCI, processed in cytoplasm, recognized by CD8 T-Cells

Exogenous Antigens

MHCII, processed in endosomes, recognized by CD4 T-Cells

T-Cell Receptor

Recognizes Antigen

CD4 or CD8 (on T-Cells)

Recognize MHC

CD4 Recognizes 

MHCII

CD8 Recognizes

MHCI

CD3 Complex

“Activation Switch” 

What are cytokine receptors needed for?

Further Signaling

Where does T-Cell development occur?

Thymus

What do surviving T-Cells mature into?

Helper T-Cells (CD4), Cytotoxic T-Cells (CD8), Gamma/Delta T-Cells

During T-Cell development, what happens to self-reactive cells?

Destroyed

During T-Cell development, what happens to TCR genes?

Rearranged

After interaction with antigen/MHC, T-Cells divide into

T helper cell 1, t helper cell 2, t regulatory cell, t cytotoxic cell

Most Prevalent Type of T Cell in Blood and Lymphoid Organs

T Helper Cells (CD4)

IL-2

Stimulates growth of B and T cells (T helper cells release)

IL-4, 5, 6

Stimulate various B cell activities

T Cell Helper 1

CD4, activated by MHC2, activates other CD4 and CD8 cells, secretes IL-2, TNF, and cytokines

T-Cell Helper 2

CD4, drives B-Cell proliferation, secretes IL-4,5,6,10 (cytokines), can dampen TH1 activity

T Regulatory Cell

CD4, CD25, involved in development of immune tolerance, suppression of pathological immune responses, inflammation, autoimmunity 

T Cytotoxic Cell

CD8, destroys a target foreign cell by lysis, requires MHC1

T Cells with CD8 Receptor

Recognize peptides presented on MHC I

Cytotoxicity

Capacity of certain T cells to kill a specific target cell

How do T Cytotoxic Cells injury target cells?

Release of Granzymes and Perforins

Granzymes

Enzymes that digest proteins

Perforins

Proteins that punch holes in membranes of cell

Apoptosis

Programmed Cell Death (caused by cytotoxic t-cells)

Superantigens

Cause non-specific activation of T-Cells

What do Superantigens result in?

Polyclonal T-Cell activation and massive cytokine release

What does a massive influx of superantigens cause?

Blood vessel damage, toxic shock, multiorgan failure