PATHOLOGY

Detailed explanation-1: -Armed helper T cells that recognize the peptide:MHC complex then deliver activating signals to the B cell. Thus, protein antigens binding to B cells both provide a specific signal to the B cell by cross-linking its antigen receptors and allow the B cell to attract antigenspecific T-cell help.

Detailed explanation-2: -The adaptive immune system mainly involves two types of white blood cells (lymphocytes) – B lymphocytes (B cells) and T lymphocytes (T cells).

Detailed explanation-3: -There are two types of specific defense. These include cell-mediated immunity and antibody-mediated immunity. Cell-mediated immunity occurs when T-lymphocytes (T-cells) become activated by exposure to pathogens. Activated T-cells then attack pathogens directly.

Detailed explanation-4: -Adaptive immune responses are carried out by white blood cells called lymphocytes. There are two broad classes of such responses-antibody responses and cell-mediated immune responses, and they are carried out by different classes of lymphocytes, called B cells and T cells, respectively.