| Summary: | Some severely immunodeficient HIV patients experience poor recovery of CD4 T-cell counts on antiretroviral therapy (ART). Evaluation of the function of thymopoiesis in T-cell production in individual patients requires a simple marker of T-cells that have recently emigrated from the thymus. Here, we address whether expression of CD31 on CD4 T-cells, CD8 T-cells, regulatory T-cells and ? T-cells correlates with other indicators of thymus function. Adult HIV-1 patients (n27) with nadir CD4 T-cell counts 100 per l and a sustained virological response to ART and healthy controls (n23) were studied. CD31 expression was assessed by flow cytometry, T-cell receptor excision circles content by real-time PCR and thymic volume by spiral computed tomography. Proportions of CD4 T-cells expressing CD45RA and CD31 declined with age in HIV patients (P0.03) and healthy controls (P0.0001), and correlated directly with other markers of thymus function. In controls, proportions of CD8 T-cells expressing CD45RA and CD31 declined with age (P0.003) and correlated directly with some markers of thymus function, but this was not seen in HIV patients. Proportions of CD45RA CD31 ? T-cells were higher in patients than controls (P0.007) and did not correlate with thymus volume. In controls, proportion of ? T-cells co-expressing CD45RA and CD31 increased with age (P0.002). These data support the use of CD31 as a marker of recent thymic origin in CD4 T-cells, but not CD8 T-cells in HIV patients receiving ART. In such patients, CD31 expression is unlikely to indicate thymic origin in ? T-cells. © 2010 Australasian Society for Immunology Inc. All rights reserved.
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