Immunity in Health and Disease

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.

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Autoimmune diseases

In general, the immune system is self-tolerant i.e. not responsive to cells or proteins of self. Sometimes, for various reasons, the immune system fails to discriminate between self and non-self. As a consequence, the cells or tissues of the body are attacked. This phenomenon is referred to as autoimmunity and the diseases are regarded as autoimmune diseases. The antibodies produced to self molecules are regarded as autoantibodies. Some examples of autoimmune diseases are:- 1. Insulin-dependent diabetes 2. Myasthenia gravis

Mechanism of Autoimmunity- Some of the epitopes of the foreign antigens are homologous(similar) to epitopes present on certain proteins of host. This results in cross reaction of antigens and antibodies which may lead to autoimmune diseases.

Organ transplantation

The phenomenon of transfer of cells, tissues or organs from one site to another (in same organism, autograft or from another organism allograft) is regarded as organ transplantation. Organ transplantation between closely related family members is preferred, since their MHCs (Major Histocompatibility Complex) are also likely to be closely related and major immunological complications can be averted.

Cancers

Growth of tumors is often associated with the formation novel antigens. These tumour antigens(oncofetal antigens) are recognised as non-self by the immune systems. However, tumors have developed several mechanisms to evade immune responses.

AIDS

Acquired Immuno Deficiency Syndrome, caused by immunodeficiency virus, is characterised by immunosuppression, secondary neoplasma and neurological menifestations.AIDS primarily affects the cell-mediated immune system which protects the body from intracellular parasites such as viruses and bacteria.