Humoral immunity is derived from the Latin word ‘humor’ meaning fluid. It is a type of immune response that is initiated by the antibodies. It involves a class of lymphocytes called the B cells which mature in the bone marrow in humans and in the Bursa Fabricius in the birds. These cells are the only ones in the immune system capable of producing the antibodies.
The antigenic receptors of the B cells are membrane-bound forms of antibodies that when interacted with by antigens result in the initiation of a sequence of B cell activation which culminates in the development of effector cells that actively secrete antibody molecules.
Antibody producing B cells differentiate into specialized forms called the plasma cells which are found only in the lymphoid organs such as the lymph nodes. They can also be found in the sites of immune response; however, they don’t occur in the blood or lymphoid circulation normally.
Humoral immunity is a cascade of processes that enables the protection of the body from pathogenic invaders. These processes include T helper cell activation which leads to the production of relevant cytokines, isotype switching, and germinal center formation, generation of memory cells, affinity maturation, neutralization of the toxins or pathogens, opsonization of the threat and promotion of phagocytic activity of macrophages.