TYPES OF IMMUNITY

Based on the type of immune cell acting against the antigens, immunity can be classified into two types-

Humoral immunity- the immunity which is mediated by antibodies produced by B-lymphocytes is called humoral immunity.
Cell- mediated immunity- The immunity which is mediated by T- lymphocytes by directly attaching themselves to the antigens is called cell mediated immunity.

During organ transplantation, tissue matching and blood group matching are essential before undertaking any graft/transplant and even after this the patient has to take immuno–suppresants all his/her life because the body is able to differentiate ‘self ’ and ‘nonself’ and the cell-mediated immune response is responsible for the graft rejection.

Based on the nature of antibodies, immunity is divided into two types-

Active immunity- When a host is exposed to antigens, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host body, this type of immunity is called active immunity. Example- antibody produced when any microorganism enters the body.
Passive immunity- When ready-made antibodies are directly given to protect the body against foreign agents this type of immunity is called passive immunity.

Example- The yellowish fluid colostrum secreted by mother during the initial days of lactation has abundant antibodies (IgA) to protect the infant.