Action of HTV in the body. After getting into the body of the person, the virus enters into macrophages where RNA genome of the virus replicates to form viral DNA with the help of the enzyme reverse transcriptase. This viral DNA gets incorporated into host cell's DNA and directs the infected cells to produce virus particles. The macrophages continue to produce virus and in this way acts like a HIV factory. Simultaneously, HIV enters into helper (T_H) T-lymphocytes (a type or subset of T-lymphocytes about which you have read above, in the immune system), replicates and produce progeny viruses. The progeny viruses released in blood attack other helper T-lymphocytes. This is repeated leading to a progressive decrease in the number of helper T-lymphocytes in the body of the infected person. During this period, the person suffers from bouts of fever, diarrhoea and weight loss. Due to decrease in the number of helper T-lymphocytes, the person starts suffering from infection due to bacteria such as Mycobacterium, viruses, fungi and even parasite Toxoplasma. The patient becomes so much immunologically deficient and unable to fight against such infections.

Action of HIV in the body cells.