Cell cycling in HIV infection: analysis ofin vivoactivated lymphocytes

Abstract

SUMMARY Infection with HIV results in increased circulating levels of T lymphocytes expressing phenotypic markers of immune activation. In the present study, using three‐colour immunofluorescence, we examined the cell cycle status of these activated cells. Activated (HLA‐DR+ CD25+ and CD38+) CD4+ and CD8+ T lymphocytes in peripheral blood were analysed for DNA content in 15 HIV + patients and 10 healthy age‐ and sex‐matched control subjects. As expected, all HIV+ patients had elevated percentage levels of activated CD4+ HLA‐DR+, CD4+ CD25+ CD8+ HLA‐DR+ CD8+ CD25+ and CD8+ CD38+ T lymphocytes compared with control subjects (P<0.001 for all). Percentage levels of CD4+ HLA‐DR+ and CD8+ HLA‐DR+ T lymphocytes in the ‘proliferative’(S‐G2M) phase of the cell cycle were also higher in the HIV+” patients compared with controls (P<0.001 for both). The percentage levels of proliferative CD4+ CD25+ CD8+ CD25+ and CD8+ CD38+ lymphocytes were, however, similar in HIV+ patients and controls, indicating that the proliferative fraction of cells in vivo was confined to the HLA‐DR+ subset and absent from the CD25+ and CD38+ populations. Four HIV+ patients had grossly elevated levels of CD8+ lymphocytes which were CD38+(>95%) and confined to the pre‐G0‐G1 phase of the cell cycle, suggesting these may be cells committed to apoptosis. These observations indicate an increase in the proliferative capacity of HLA‐DR+ T lymphocytes in HIV infection in vivo. The reduced DNA content in other populations (e.g. CD38+ CD8+ lymphocytes) of some patients with advanced HIV disease suggests that these cells are apoptotic. Thus our results define both proliferative and apoptotic processes as a spectrum of activation‐related events in HIV infection.

The CD8+HLA‐DR+ T cells expanded in HIV‐1 infection are qualitatively identical to those from healthy controls

“…Although activated cells might be more likely to undergo proliferation, it has been reported that CD8 + HLA‐DR + T cells are at an arrested phase of cell cycle and unable to divide . In order to determine the cell cycle position of CD8 + HLA‐DR − naive, CD8 + HLA‐DR − memory, and CD8 + HLA‐DR + cells and test the accuracy of those statements, simultaneous staining with 7‐amino‐actinomycin D (7‐AAD) (DNA) and pyronin Y (RNA) was performed (Fig.…”

“…It has been reported that CD8 + T cells from HIV‐1 infected individuals are at an arrested phase of cell cycle and unable to divide . Increased expression of G1 cyclin‐dependent kinase inhibitors: p16, p21, or p27 are responsible for cell cycle arrest at G1 .…”

“…A number of studies have demonstrated that CD8 + T cells obtained from patients with HIV‐1 infection are more prone to apoptosis and less responsive to anti‐CD3 stimulation than CD8 + T cells from uninfected individuals when stimulated in vitro . The mechanism(s) underlying these observations have been difficult to dissect.…”

Measurement and Analysis of Lymphocyte Deformation in Microchannel Contraction Flows Using a Compound Drop Model

“…White blood cells (WBCs) have received little attention, despite their key role in the immune system [11,12] and that defects of WBCs are associated with a number of severe diseases [13]. Characterization of the physical properties of WBCs is therefore important not only to understand the flow and transport phenomena within blood vessels, but also potentially in the diagnosis of WBC-associated diseases and developing the technologies for single cell analysis.…”