Tag: zoology

There are 2 forms of MHC, namely MHC class I and class II proteins. They play important role in the adaptive immunity. They present peptides on the cell surface for recognition by T cells. Helper T cells are part of adaptive immunity. They recognize and activate B cells to secrete antibodies and macrophages to destroy foreign bodies. They also help activate cytotoxic T cells to kill infected target cells. B cells are part of humoral immune response. They recognize soluble antigens. Antigen-presenting cell (APC) are those cells with detects, engulfs and digests antigen. 

IgD provides the activation signals to the B cells by acting as antigen receptors on the B cell surface. The B cells on being activated begins the immune defense mechanism of the body. So, the correct option is 'IgD'.

B cells, also known as B lymphocytes, are a type of white blood cell of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system by secreting antibodies. BCRs allow the B cell to bind to a specific antigen, against which it will initiate an antibody response. They provide immunity by producing antibodies.

So, the correct option is 'producing antibodies'.

T cells (thymus cells) and B cells ( bone marrow- or bursa-derived cells) are the major cellular components of the adaptive immune response. T cells are involved in cell-mediated immunity, whereas B cells are primarily responsible for humoral immunity (relating to antibodies).

Organ transplant rejection is primarily a cell-mediated immune response. Cytotoxic T cells (CD8+ T cells) recognize foreign MHC molecules on the transplanted tissue and destroy the cells.

T-lymphocytes are produced in bone marrow but differentiated in thymus glands. T lymphocytes play a central role in cell-mediated immunity. They can be distinguished from other lymphocytes, such as B cells and natural killer cells by the presence of a T-cell receptor  on the cell surface. They are called T cells because they mature in the thymus.

Associated lymphoid organs are composed of lymphoid tissue, and are the sites either of lymphocyte production, or of lymphocyte activation.

Clonal selection is a process to determine how B or T cell recognizes an antigen that enters the body is selected from the per-existing cell pool of differing antigen specificities and its proliferation to generate a clonal cell population that eliminates the antigen.
Thus, the correct answer is option B.