MKI67 and HIV infectious disease: Although previous studies of Ki67 expression have suggested that naïve cells may be brought into cycle as a homeostatic response to falling CD4 cell numbers in HIV infection,[18], [34] we did not observe any correlation of naïve cell turnover with absolute CD4 count in this study (possibly because we selected subjects with relatively high CD4 counts) but we did observe a trend with rate of CD4 decline and viral load, surrogate markers of immune activation.