Question

One of the major hallmarks of the adaptive immune response is the specificity in activating only those appropriate T and B cells to respond to the pathogen/antigen. Please discuss how the “3 cell model” of APC, T cell, and B cell ensure and maintain the specificity so that only antigen-specific cells are activated.

Answer 1

Answer)

1. T-cells: It is also called as a T-lymphocytes and main component of adaptive immunity

Functions: It main role is defence against intracellular viruses, pathogens, bacteria. Hence, it involved in the cell mediated immune reponse

Production: T-cells originate from haematopoietic stem cells in the bone marrow. These stem cells divided into myeloid and progenitor cells. This cells differentiate into T and B-cells

Types: There are 4 types of T-cells

a. Th cells: it helps in maturation of B-cells into plasma cells and memory cells and they major role in activation of cytotoxic T-cells and macrophages

They become activated when they are presented MHC-II molecules which also expressed in APC (Antigen presenting cells) and cytokines released and destroy antigen.

b. Tc cells: CD8+ cells can be recongize by Tc cells and causes virus infected and tumour cells. These cells recongize MHC-I molecule which are present in nucleated cells on their surface.

c. Memory cells: It provide memory against previously encountered virus. These cells may be either CD4+ or CD8+ cells

d. Natural killer cells : It is mainly involved in the innate immunity response. Function of these cells similarly to T-cells.

2. B-cells: B-cells produces plasma and memory cells. The plasma cells turn produces large amount of immunoglobulins specific for antigens. Usually, IgM is more effective for pathogen and IgG antibody

Memory B cells produces involved in secondary immune reponse. Therefore, B-cells involved in hummoral immunity whereas T-cells involved in cell-mediated immunity

3. APC (Antigen Presenting cell)

Role:

a. It involved in Phagocytosis

b. Processing antigen is required for T-cells and B-cells