The prime function of immune system is to protect the host against the invading pathogens. The body tries its best to overcome various strategies of infectious agents (bacteria, viruses), and provides immunity. Some of the important immunological aspects in human health and disease are briefly described.

ORGAN TRANSPLANTATION

The phenomenon of transfer of cells, tissues or organs from one site to another is regarded as organ transplantation. In case of humans, majority of organ transplations are allografts (between two individuals). The term xenograft is used if tissues/organs are transferred from one species to another e.g. from pig to man.

Other transplation is associated with immunological complications, and tissue rejection. This is because the host body responds to the transplanted tissue in a similar way as if it were an invading foreign organism. Major histocompatibility complex (MHC) is primarily involved in allograft rejection. This is due to the fact that MHC proteins are unique to each individual, and the immune system responds promtly to foreign MHCs.

Organ transplatation between closely related family members is preferred, since their MHCs are also likely to be closely related. And major immunological complications can be averted.