Page 135 - MNU microbiology theoritical 2025

General Microbiology & Immunology (PM 401) Second level Semester 4 2024/2025

Type of T- cells

• Helper T cells:

• detect infection and secretes signals (cytokines) that trigger the

proliferation of both T cells and B cells.

• These cells are neither phagocytic nor cytotoxic and cannot kill

infected cells

• So they provide help to other cells of the immune system in mounting immune

responses by causing cell activation or the secretion of cytokines.

• Helper T cells express a unique antigen marker on their surface called CD4 and

they have receptors that bind proteins displayed by class II MHC molecules.

Cytotoxic T (killer):

• the true effector cells in cell-mediated immunity.

• These cells secrete granules containing chemicals that destroy a

targeted cell

• express a unique antigen marker on their surface called CD8.

• bind to protein fragments displayed by class I MHC molecules.

Suppressor T (Regulatory): help distinguish between self and nonself

molecules, reduce the risk of autoimmune diseases.

Memory T: A long-lived B cell or T cell that has previously recognized

a threat (antigen) and “remembers” the antigen. When the same threat appears

again, the memory cells are ready to produce a much faster immune response and

eliminate the threat.

General Microbiology & Immunology (PM 401) theoretical handbook Page 124