How does AIDS avoid the immune system?
Human Immunodeficiency Virus (HIV) that causes AIDS attacks the most important cell of the immune system itself, ultimately overpowering the immune system.
The binding of HIV with the target cell is through the receptor mechanism. The gp120 of the virus envelope will specifically bind with the CD4 molecule on the surface of target cells. Thus CD4 acts as a receptor for the virus.
The CD4 molecules are present on the surface of T-helper cells and therefore helper cells receive maximum attack from HIV. T Helper cells influence the B cells to proliferate and secrete antibodies. Thus both cell mediated immunity and antibody mediated immunity are compromised by attack of HIV .
Macrophages, monocytes and glial cells are also susceptible for HIV entry and propagation. Macrophages act as reservoir of the virus.
The virus has an extraordinary rate of replication; over 10 million particles are produced per day inside the host. The infected host cell lives only for a day and half.
The T-helper lymphocytes decrease in number, leading to immunodeficiency. This decrease leads to suppression of almost all the immunological effectors. The macrophages and monocytes, acting as reservoirs for HIV virus, disseminate the virus to various organs, including the Central Nervous System.
Antibody response against a foreign antigen becomes poor. Lymphokines such as interferon, interleukin-2 are lowered.
When all the mechanisms of immunity are thus paralyzed, opportunistic pathogens get entry in to the body.