Dear Doctor

What is CD4 count? What are the likely effects of using ARVs? Maggie

Dear Maggie,

CD4 cells (also known as T4 or helper T cells) are lymphocytes (a type of white blood cell), which are key in both humoral and cell-mediated immune responses. These are the main target cells for HIV virus. Their numbers decrease during HIV infection, thus reducing the ability of the body to fight diseases. Their level is used as a marker of progression of the infection. As per the level of CD4 count, the person may be healthy or have minor sickness like skin infections or repeated upper respiratory tract infections. With decrease in CD4 count, he/she becomes susceptible to serious infections like pneumonias or oral thrush. As the CD4 count comes to very low levels, person becomes prone to life threatening infections or cancers. A low CD4 count, in spite of taking ARV drugs regularly is an indication to consider drug resistance, review the combination of drugs and change it if necessary.

ARV drugs block the attachment of HIV virus to CD4 cells or check its multiplication through different mechanisms. This helps in reducing the viral load and also builds up the immunity of the person. Improvement in the CD4 count is a marker of a good response to ARV drugs being given. However in spite of ARV drugs the CD4 count may not improve, if there is primary resistance to the drugs. If the individual takes the drugs irregularly, he is likely to develop secondary resistance, i.e. drugs which were effective initially cease to be effective. If the drugs are started when the CD4 count is already very low, they may not be very effective in helping the person to combat diseases.