Active: Generated by the body after exposure to an infection or a vaccine, e.g., antigens
Passive: Donated to the body transplacentally, or through injection of antibodies
It is where lymphocytes develop, and they are divided into:
Central: Where cells are formed:
T lymphocytes are formed in the Thymus.
B lymphocytes are formed in the liver during the fetal period, and in the bone marrow in adults.
Peripheral: Where cells are expressed. This takes place in the spleen, lymph nodes, tonsils, and Peyer’s patches.
Cell-mediated immunity (CMI): It is the job of T lymphocytes, natural killer (NK) cells, and macrophages, which are destined to kill the organism and its aberrant host cells.
Humoral immunity: It is the job of B lymphocytes, which produce antibodies.
Major Histocompatibility Complex (MHC)
The MHC is a cluster of genes found in every human and animal cell. It is known as human leukocyte antigen (HLA) in humans, and is located on chromosome 6.