CD4 immunodeficiency and increased viral load has been noted as the hallmark of HIV infection, with leucopenia and lymphopenia being documented in different proportions in HIV-positive patients.[19] The CD4 count normal range is between 500 and 1500 cell/mm and when left untreated, levels can drop below 200 cell/mm which is one indication for diagnosis of AIDS. Here, CD4 is linked to lymphopenia.