Use of a flow cytometric assay to quantitate apoptosis in human lymphocytes.

Apoptosis is an active process of cellular self-destruction which plays an important physiologic role in the maintenance of homeostasis. This form of cell death has classically been assessed by the appearance of a "ladder-like" banding pattern upon gel electrophoresis of disrupted cells. The electrophoretic method is qualitative but offers no means of quantitation. We have optimized a flow cytometric method which allows quantitation of the apoptotic subset of cells. This assay uses propidium iodide and therefore can be performed on any flow cytometer with a blue-green excitation line. We initially verified the results of this method by using human thymocytes treated with dexamethasone, a known inducer of apoptosis. Gels were run simultaneously with flow cytometric analysis and assessed for the presence or the absence of apoptotic cells. Results obtained with gel electrophoresis correlated well with the flow cytometric method. In further studies, we applied this assay to human PBMC and obtained similar results. In conclusion, this assay is a significant improvement over currently available methodology for the determination of apoptosis. We have found it to be quantitative, reproducible, and applicable to different human cell types. The role of apoptosis in human disease remains to be elucidated and this method offers a convenient means to study this process.

Accelerated apoptosis in peripheral blood mononuclear cells (PBMCs) from human immunodeficiency virus type-1 infected patients and in CD4 cross-linked PBMCs from normal individuals.

This study investigates apoptosis as a mechanism for CD4+ T-cell depletion in human immunodeficiency virus type-1 (HIV-1) infection. Although several recent studies have shown that T cells of HIV-infected individuals show enhanced susceptibility to cell death by apoptosis, the mechanisms responsible for apoptosis are largely unknown. By using a flow cytometric technique and by morphology, we have quantitated the percentage of cells undergoing apoptosis in peripheral blood mononuclear cells (PBMCs) from HIV-seronegative donors and from HIV-infected asymptomatic patients. The PBMCs were cultured without any stimulus or with staphylococcus enterotoxin B, anti-T-cell receptor (TCR) alpha beta monoclonal antibody WT-31, or phytohemagglutinin for periods up to 6 days. In addition, we sought to determine whether cross-linking of CD4 followed by various modes of TCR stimulation in vitro could induce apoptosis in normal PBMCs. Here we show that (1) patient PMBCs undergo marked spontaneous apoptosis; (2) stimulation of T cells of patients as well as normal donors results in increased apoptosis; and (3) cross-linking of CD4 molecules is sufficient to induce apoptosis in CD4+ T cells if cross-linking is performed in unfractioned PBMCs, but not if CD4 molecules are cross-linked in purified T-cell preparations. These observations strongly suggest that accelerated cell death through apoptosis plays an important role in the pathogenesis of HIV-1 infection. At the same time, our observations implicate cross-linking of CD4 in vivo as a major contributor to this mechanism of accelerated cell death in HIV infection.

Acquired ichthyosis in concomitant HIV-1 and HTLV-II infection: a new association with intravenous drug abuse.

BACKGROUND: Papulosquamous eruptions are common in HIV-1-infected patients. Acquired ichthyosis may occur after profound T-cell depletion. Intravenous drug users infected with HIV-1 can be coinfected with human lymphotropic virus II (HTLV-II). OBJECTIVE: We examined the relation between acquired ichthyosis and concomitant infection with HIV-1 and HTLV-II in intravenous drug users. METHODS: We examined 184 male and female HIV-1-positive intravenous drug users for acquired ichthyosis. Enzyme-linked immunosorbent assay was used to screen these patients for antibody to HTLV-I/II. Western blot, viral isolation, and the polymerase chain reaction were used to confirm that serologic responses were from HTLV-II and not HTLV-I. RESULTS: Acquired ichthyosis occurred in 6.3% of white, 16.4% of Hispanic, and 21.7% of black patients. It occurred only after profound helper T-cell depletion, in association with increasing age, and with concomitant infection with HTLV-II (22.2% vs. 6.8% in HIV-1 singly infected patients [p < 0.038]). CONCLUSION: Acquired ichthyosis may be a marker of concomitant infection with HIV-1 and HTLV-II in intravenous drug users and occurs after profound helper T-cell depletion.

Syndrome of severe skin disease, eosinophilia, and dermatopathic lymphadenopathy in patients with HTLV-II complicating human immunodeficiency virus infection.

Two intravenous drug users dually infected with human immunodeficiency virus type 1 (HIV-1) and human T-cell leukemia virus type II (HTLV-II) developed an unusual severe dermatitis characterized by progressive brawny induration, fissuring, and ulceration of the skin, with an associated CD8 cell infiltration in one patient. Both patients had persistent eosinophilia. Lymph node biopsy revealed dermatopathic lymphadenopathy, an unusual pathologic finding in HIV-1 infection but one seen in association with mycosis fungoides and other skin disorders. Two new isolates of HTLV-II virus were established from these patients and were identified as HTLV-II by Southern blotting. This type of skin disease and lymph node pathology has not been found in other intravenous drug users who have been infected with HIV-1 alone or in patients in other risk groups for HIV-1 infection. HTLV-II may play a role in this unique new disease pattern in patients infected with HIV-1.