How does HIV damage our immune system?
In a newly HIV-infected person, the virus enters some of the CD4 lymphocytes, which produce many new copies of the virus and shed them into the body. The CD4 lymphocytes eventually die as they release their load of viruses. The new copies of HIV circulate in the body and attack other CD4 lymphocytes, which in turn produce more HIV and then die. This goes on and on — more and more CD4 lymphocytes are destroyed, as more and more HIV copies are made.
What effect will the destruction of many CD4 lymphocytes have on the immune system's ability to protect the person from other infections?
The CD4 lymphocytes give essential help to the other types of lymphocytes that make antibodies, or kill virus-infected cells in the body; without this help, the rest of the immune system cannot function properly.
Over time, the number of CD4 lymphocytes declines to the extent that the immune system cannot protect the person from illnesses like chest infections and diarrhoeal diseases that it would normally fight off. We will return to this point shortly.