Q: I came across an article related to AIDS where it was stated that the defence mechanism cell count (CD4 count) in HIV-positive patients is lower than the average. For e.g. an HIV infected person will have a CD4 count of 800 where as the CD4 count of a healthy person will be 1000. What I would like to know is, apart from being infected with HIV, can the defence mechanism cell count/CD4 decrease even due to some other diseases or virus? Or is HIV the one and only cause of lowering the CD4 count of a person?

A:About 5% of healthy persons in a normal population may have abnormal CD4 cells counts, and in a subgroup of patients, the low T-cell numbers or ratios appear to be stable. Thus, in the absence of a history of a specific infection or illness or major abnormalities on physical examination, it is not worthwhile to attempt to find a specific cause for the abnormality of T-cell subsets. It has been found that low CD4 counts are a common reaction to many kinds of physical and psychological stressors and are associated with a variety of conditions, including many viral infections, bacterial infections, parasitic infections, sepsis, tuberculosis, coccidioidomycosis, burns, trauma, intravenous injections of foreign proteins, malnutrition, over-exercising, pregnancy, normal daily variation, psychological stress, and social isolation.