Question

A. "Clonal selection" applies to which type of leukocytes? B. In which part of the body do the earliest stages of lymphocyte development occur? C. What event "triggers" the development of the cell to an activated cell? D. In what part(s) of the body does this triggering event typically take place?

Answer 1

A. Clonal selection is a study which deals with immunology that explains the functions of cells i.e., lymphocytes of the immune system in response to specific antigens invading the body where specific B or T-helper lymphocytes are selected to undergo clonal expansion.

B-lymphocytes and T-helper lymphocytes have unique and specific antigen receptors on their cell surface membranes which consists of different type of antigen receptor.

B-lymphocytes create unique antibodies that target the specific antigens on pathogens and destroy them to fight the infection.

Mature T and B cells are functionally heterogeneous populations of lymphocytes which exhibit complex migratory patterns and that occupy discrete anatomical compartments within the lymph nodes, spleen, and other lymphoid tissues.

And these T lymphocytes initiate cell-mediated immunological reactions, whereas B lymphocytes initiate antibody-mediated immunological reactions.

B.  Earliest stages of Lymphocyte development occurs in Bone marrow and Thymus

C. T- cell activation is critical for the initiation and regulation of the immune response. Activation of T cells leads to the development of cell-mediated immune mechanisms through the action of cytotoxic T cells (CD₈) as well as by the engagement of accessory cells including macrophages.

It also increases the antibody responses through the action of T-helper cells (CD₄) and the enhancement of antibody production by B cells.

The B cell is activated by two different signals the first signal is from the antigen receptor which is the major signal few of the cells diffrentiate into plasma cells and produce antibodies while few turn out to be long lived memory B cell which are stimulated later by the invasion of the antigen and the second signal is from either thymus dependent or thymus independent antigens.

D. The triggering event typically take place mainly in secondary lymphoid organs i.e., lymph nodes and spleen.