Immune system

Question 1

What event triggers the release of histamine from mast cells in an allergic reaction?

Answer 1

binding of an allergen onto a specific IgE antibodies attached to mast cells triggers the mast cells to release histamine.

Question 2

What makes HIV particularly hard for the immune system to defeat?

Answer 2

HIV is particularly hard for the immune system to defeat because (1) it destroys helper T cells, which are key players in adaptive immunity and (2) is has a high mutation rate and so it rapidly becomes resistant to drugs.

Question 3

Which proteins must be carefully matched before an organ transplant?

Answer 3

MHC proteins and blood type antigens (ABO,etc) are carefully matched before an organ transplant.

Question 4

Describe the killing mechanism of cytotoxic T cells that involves perforins.

Answer 4

The cytotoxic T cell releases perofrin and granzymes onto the identified target cell. Perforins form a pore in the target cell membrane, and granzymes enter through this pore, activating enzymes that trigger apoptosis(cell suicide).

Question 5

Which type of T cell is most important in both cellular and humoral immunity? Why?

Answer 5

Helper T cells are central to both humoral and cellular immunity because they are required for activation of both cytotoxic T cells and most B cells.

Question 6

What happens when antigens are bound in the absence of co-stimulators?

Answer 6

Binding of antigens in the absence of co-stimulators causes the lymphocyte to develop anergy- a state of permanent unresponsiveness to that antigen.