Hello, everyone, Following a last discussion on the List about CD45RA and memory cells, Philippe Poncelet and I would like to share with you some observations we made in quantifying the expression of Fas receptor (CD95) on HIV-infected patients. We used our recently commercialized APOCYT Fas (Cell) kit. This is another of our Quantitative Flow Cytometry application kits. Healthy donors express 2 very well defined subsets of T-lymphocytes. The first one is a Fas (low) population expressing less than 2,000 Fas per cell. The second subset is Fas (high) with over 2,000 up to 20,000 Fas per cell. The distinction between both supopulations is very easy when using quantitative flow cytometry and since the reproducibility of our kit is remarkable, we were able to define the 2,000 value as a differentiation criteria between the subsets. The relative distribution of both subpopulations looks rather similar to that of CD45RO (low) and CD45RO (high). According to the literature Fas (high) T cells proportion increases with age and the Fas (high) phenotype is often related to chronically activated/memory T cells. Then we measured the expression of Fas on T cells from HIV-infected patients and found that only Fas (high) T cells were present in the samples of the small series we tested. Since the literature describes significant, although low, residual CD45RA+ T cells in HIV patients, we wonder whether the absence of Fas (low) T cells could be explained by the few remaining CD45RA+ being activated/memory T cells. Silly question, may be: could high expression level of Fas also be a valuable marker for memory cells? By the way we also tested few bone marrow transplant patients using APOCYT Fas (cell) and also found a majority of Fas (high) T (CD3-PE+) lymphocytes. Anyone with thoughts and comments about these results? Happy Holiday Season and Greetings from France Michel Canton, PharmD Philippe Poncelet, PhD BioCytex Tel: +33 (0) 4 91 94 29 39 Fax: +33 (0) 4 91 47 24 71
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