Question

1. Describe the two adaptive immune responses (B cells and T cells) that respond to changes in cells in our body such as infections or cancer.

Answer 1

An adaptive immunune system is that which combats any non-self antigens through cell mediated and humoral response mechanisms. Cell mediated and humoral response is carried out by T cells and B cells respectively. Naive B and T cells have membrane bound antibodies. On the other hand APC (antigen presenting cells) engulf the antigen and present their different epitopes on their surface. When the membrane bound antibodies bind to these epitopes they get activated. Specific antigenic epitopes are identified by the naive B cells. Further the activated B cell becomes an effector cell (plasma cell) or clonal expansion so that the cells produce antibodies towards that particular epitope present on the antigen. Subsequently, the antibodies produced against the particular epitope binds to the antigen even if they are freely suspended in the host body. After the antigen is removed from the system some of the B cells beocme memory cells which will come into act if the antigen comes into contact the next time. On the other hand, T cells would bind to the antigenic epitope only if it is attached to a MHC receptor. Once T cells are activated it gives rise to other subtypes namely; Helper T cells, Cytotoxic T cells and regulatory T cells. Helper T cells activate other immune cells such as cytotoxic T cells, B cells. Cytotoxic B cells attaches to the affected cells and removes pathogens and infected host cells. Regulatory T cells regulates the cells to differentiate between host molecules and antigenic moieties so that host immune system do not become autoimmune.