Function of The Immune System
The function of the immune system is to protect the body from foreign invading pathogens, such as bacteria, viruses, toxins and parasites that may inhibit the body and cause harm and disease. The immune system is able to carry out this function by having the ability to distinguish between “self” and “non-self”by the presence of a specific MHC marker on the surface of all "self" cells (except non-nucleated cells e.g. red blood cells). Any substances distinguished as “non-self” will stimulate an immune response in the body.
Components of The Immune System
How The Immune System Works in a Healthy Body
In a healthy body, the immune system is able to detect invading foreign pathogens as “non-self” cells, which triggers an immune response from the body. When a pathogen enters the body, complement attaches to the pathogen to act as a marker to assist phagocytes in recognising pathogens in the body. Once phagocytic cells detect the foreign substances, the substance is engulfed by the macrophage in a vesicle. The vesicle will then fuse with lysosomes and digest the substance. Antigenic fragments of the substance are combined with an MHC marker and displayed on the surface of the macrophage to alert other white blood cells of the invading pathogen. The antigen is then presented to T helper cells, which present the antigen to immature B cells. The immature B cells then undergo colonial expansion to produce plasma B cells and several memory B cells. Plasma B cells produce antibodies that are specific to the antigen whilst memory B cells remain in the lymph in case of future reencounter of the same antigen. If the antigen is encountered again the process to produce antibodies will be much quicker as the process of engulfment, presenting to T cells and immature B cells does not need to occur, due to the memory B cell present in the lymph.