The immunity mediated by the antibodies that released into the fluids of the body (humors) such as plasma, lymph etc., is called humoral immunity.
Mechanism of humoral immunity: Whenever the antigen (exogenous) enters into our body, they reach secondary lymphoid organs, where the free antigens bind to Fab end of the membrane bound antibodies that are present on the surface of mature B-cells. They engulf and process antigen. Then they display the antigenic fragments on their membrane with the help of Class-II MHC molecule. Then appropriate `T_(4)` cells recognise them and interact with the antigen-MHC-II complex and release interleukins, which stimulates the B-cells to proliferate and differentiate into memory cells and plasma cells, The plasma cells release specific antibodies into plasma or extra cellular fluids.
These antibodies help in opsonising and immobilizing the bacteria, neutralizing and cross linking of antigens leading to agglutination of insoluble antigens Mechanism o and precipitation of soluble antigens. They also activate the phagocytes and complement system.
