Page 133 - MNU microbiology theoritical 2025

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

Composition

The adaptive immune response is divided into two systems:

-The humoral system works to eliminate antigens that are extracellular (not

within a host cell), for example, bacteria, toxins, or viruses in the bloodstream

or in tissue fluids.

-The cellular system deals with antigens residing within a host cell, such as a virus

that has infected a cell

Cells of adaptive immune system

The cells of the adaptive immune system B cells and T cells are the major

types of lymphocytes.

Development of B and T cells

B cells (and T-cells) are produced by stem cells in the bone marrow.

B cells T Cells

• Mature in Bone marrow. They travel in the bloodstream to the

Thymus where they mature in.

Involved in humoral immunity Involved in cell-mediated immunity

• Once activated by antigen, divide in • Activated when another cell presents

blood and secondary lymphatic organ antigen to them.

into two types of cells: • They are of several types:

➢ Plasma cells that secrete antibodies ➢ Cytotoxic T cells (killer T cells)
➢ Helper T cells
➢ Memory cells.
➢ Suppressor T cells
➢ Memory T cells.

General Microbiology & Immunology (PM 401) theoretical handbook Page 122