Molecular Basis of Ag Recognition

Question 1

T cell receptors need to bind to MHC AND need a stimulatory signal from the APC

Answer 1

True

Costimulation involves a protein B7 on APC and protein CD28 on T cell

Question 2

There are adhesion molecules to keep T cell and MCH together

Answer 2

True

TCR/MHC
B7/CD28 (CTLA-4)
Adhesion pair LFA-1/ICAM-1

Question 3

Non-traditional T cells

Answer 3

γ and 𝛿 T cells are relatively few, are in epithelial tissues

T cell repertoire is limited

Directly activated without APCs

No memory cells

Role in recognizing lipid antigens

Question 4

B cells become plasma cells

Plasma cells are found in lymphoid organs (not in plasma)

Can present Ag to T cells

CD19, coreceptor for BCR, is a marker of B cells

Answer 4

True

Question 5

B cell receptors don’t need APC

Answer 5

True

Question 6

BCR

Answer 6

2 light, 2 heavy chains

Surface Ig (IgM or IgD)

Question 7

2 mechanisms for activating B cells

Answer 7

1. Antigens activate B cells with help of T helper cell (called Thymus Dependent or TD Ags)
2. Lipids, carbs, polynucleotides activate B cells without help of T cells and are called “Thymus Independent” or TI Ags

Question 8

B cell activation via thymus dependent (TD)

Answer 8

Antigen binding to B cell receptor and delivers the first signal to B cell

Helper T cell delivers 2nd signal via CD40 ligand and cytokines

B cell proliferates and differentiates into plasma cells

Question 9

B cell activation via thymus independent (TI)

Answer 9

B cell receptors are activated by cross-linking with antigens

Multiple receptors on B cell bind to the antigen at once and this causes cross-linking, which makes a signal

Signal is transduced by Igα and IGβ

Question 10

B cell activation needs both interleukins and CD40 to make it go and become a plasma cell

Answer 10

True

Question 11

Polysaccharides do not bind to class II MHC proteins, but peptide antigens do

Answer 11

True