ALTERED LYMPHOCYTE ANTIGEN EXPRESSIONS IN HIV-INFECTION - A STUDY BY QUANTITATIVE FLOW-CYTOMETRY

To identify surface antigen changes that may contribute to the immune deficiency in infection with the human immunodeficiency virus (HIV), w e quantified, by double-staining flow cytometry, the number of antigen s of the main peripheral blood lymphocyte subsets from 30 HIV-positive persons and compared them with those of 19 HIV-negative healthy donor s. Standard microbeads with different capacities to bind mouse immunog lobulins were used to convert the mean fluorescence intensity values i nto numbers of antigen molecules per cell, measured as antibody bindin g capacity. The level of expression of different lymphocyte antigens i n HIV-infected patients differs from that seen in normal blood lymphoc ytes. Some of these surface markers are decreased, whereas others are increased, and their expression is modulated depending on the specific cell subset considered. The expression of CD3, CD4, and CD8 on T lymp hocytes is significantly decreased; moreover, CD3 is down-regulated on activated and nonactivated T lymphocytes and on CD4 and CD8 cells. In contrast, the expression of CD2 on T cells is significantly increased . Natural killer cells exhibit down-regulation of CD7, normal levels o f CD8 and CD56, and overexpression of CD2. Our results also identified , for most of these antigens, quantitative differences in membrane exp ression according to different disease stages, as assessed by the CD4 T-cell count. Quantitative flow cytometry therefore may provide useful insights into the lymphocyte functional defects characterizing HIV in fection.