CD80 expression is decreased in hyperplastic lymph nodes of HIV+ patients

A centrofollicular hyperplasia is present within secondary lymphoid organs during all the asymptomatic phase of the HIV disease. Although this hyperplasia has been well characterized by histological studies, the nature of the phenotypic alterations in B cell populations occurring within HIV+ lymphoid organs remains to be established. By immunohistochemistry, we thus investigated whether a particular germinal center (GC) B cell population was increased during HIV-induced hyperplasia and whether any phenotypic change was specific to HIV-1 infection. As compared to normal tonsils (three cases) and HIV- hyperplastic lymph nodes (eight patients), we observed a loss of GC polarization in all HIV+ sections (11 patients), with no more delineation between dark and light zones, as shown by Ki67, CD10, CD77, CD95 and CD86 staining. In contrast to CD86 expression which remained as intensive in HIV+ as in HIV- lymph nodes, CD80 staining was strongly decreased in GC of HIV+ lymph nodes but not in their extrafollicular zones. The loss of CD80 expression from CD19+ B cells was also observed by cytometric analysis of cell suspensions of three HIV+ patients. Although we found no evidence of an increase in a particular GC B cell subset in HIV-1-induced hyperplasia, the strong GC disorganization observed may induce impaired cell-cell interactions and thus participate in the loss of CD80 antigen. In contrast to HIV- situations where CD80 and CD86 was similarly expressed on B cells, the lower level of CD80 expression in HIV+ GC may favor Th2 T cell responses through CD86-CD28 interactions.