T Lymphocytes and Cell-mediated Immunity

Question 1

What is an antigen?

Answer 1

An antigen is any part of an organism or substance that is recognised as non-self by the immune system and stimulates an immune response.

Question 2

What are the two main types of lymphocyte?

Answer 2

B-LYMPHOCYTES
-They mature in the ‘B’-one marrow
-Associated with the humoral response
-Antibodies present in fluids

T-LYMPHOCYTES
-They mature in the ‘T’-hymus gland
-Associated with the cell-mediated response
-Body cells

Question 3

What is the role of T-cells (Lymphocytes) in cell-mediated immunity?

Answer 3

-After phagocytosis, some of the pathogens antigens will be present on their surface
-Receptors on certain helper T cells fit exactly onto these antigens
-This attachment activates the T cell to divide rapidly by mitosis and form multiple clones

Question 4

What can cloned T cells undergo? (After clonal expansion)

Answer 4

The cloned T cells can then undergo the following:
(1) Develop into memory cells enabling a rapid response to future infections
(2) Stimulate phagocytes to engulf pathogens by phagocytosis
(3) Stimulate B cells to divide and secrete their antibodies
(4) Activate cytotoxic T cells