Immunology is the branch of biology that deals with the study of the immune system, its mechanism, types, and mode of action.
The immune system is the body’s defense mechanism that triggers response against any foreign particle that has not been previously encountered and helps to combat infections or diseases. The immune system that was present before the birth of a person is called the innate immune system and the system that learns as the person grows and becoming more efficient in recognizing the pathogens as time passes on, is the acquired immune system.
Immune cells have the capacity of the self, non-self discrimination. Tolerance to self-antigen and effector functions against foreign antigen either by the production of antibodies (humoral immunity) or by effector T cells (cell-mediated immunity) is the main function of immune cells.