Blood Bank Lecture 4 T CELLS Adaptive Immunity

What are the two main branches of Adaptive Immunity?

Cell-mediated Immunity = T cells

HuMoral Immunity = B cells + antibodies

What is the first step of Tcell maturation?

Double Negative Stage

Negative for both CD4- and CD8-

In the Double negative stage, what are immature T cells called?

Thymocytes

What is the main purpose of the Double Negative (First step) Stage?

Building the BETA chain of the TCR (T-cell Receptor)

TCR = Beta and alpha chains

What is the second step of T cell maturation?

Double Positive stage because the T cell expresses both CD4+ and CD8+ now

What are the 3 main things happening in the second step of T cell maturation (Double Positive)

1. CD4+ and CD8+ expression

2. Alpha chain is built

3. TCR is tested to see how well it recognized MHC

What are the two cases where a thymocyte will be destroyed in the Double Positive stage (2nd step)?

Binding is too strong

No binding

APOPTOSIS OCCURS

What is the purpose of the TCR

The part of the T cell that allows it to recognize its specific antigen

composed of an alpha and beta chain

What is the third step in T cell maturation?

Single Positive Stage

Either CD4+ or CD8+

What are the 2 main things happening in the Single Positive step (3rd)?

1. T cell differentiation, either CD4+ or CD8+ active

2. Checks if it BINDS SELF ANTIGEN

What are the final 2 types of Mature T cells?

CD4+ = T helpers and T regulatory

CD8+ = cytotoxic T cells

How does a T-cell response begin?

Antigen Presenting cell is activated → T cell interacts with the APC → Adaptive response → T cells differentiate

Once the adaptive response is activated, which 2 different cells can CD4+ T cells differentiate into?

1. T helper

2. T regulatory cell - which prevent a overactive immune system

What are the 3 different types of T helper cells (CD4+)

Th1 = activate CD8+ cells

Th2 = Help B cells w antibody production

Th17 = recruit granulocytes (fighting infections)

What do T regulatory cells do (CD4+)?

secrete INHIBITORY CYTOKINES to inhibit the immune response

Inhibit too many T cells

What do Cytotoxic T cells do (CD8+)

Bind to an antigen

secrete ENZYMES that kill the cell

Where does T cell maturation occur?

Thymus