White cell subsets in apheresis and filtered platelet concentrates.

BACKGROUND: White cell (WBC)-reduced platelet concentrates (PCs) are defined by their absolute WBC count, a criterion which provides no information regarding the various WBC subsets contained in the PC. These heterogeneous cells are known to mediate different physiologic and pathophysiologic functions and account for distinct adverse transfusion responses. This study describes a method which allows the detection and quantification of these subsets and characterizes their presence in a variety of platelet components. STUDY DESIGN AND METHODS: Random-donor pooled PCs (RD PCs) and single-donor apheresis PCs (SD PCs) were studied. RD PCs consisting of 6 units of 2- to 3-day old PCs were randomly assigned to be filtered with one of four WBC-reduction filters from three different manufacturers (n=34). The residual WBCs were pelleted by centrifugation and isolated on a density gradient. The various WBC subsets were quantified by flow cytometry in unfiltered and filtered PCs using fluorescence and two-angle light scatter. SD PCs obtained with two manufacturer's systems and three processing protocols (n=30) were studied in like manner. RESULTS: WBC counts for non-WBC-reduced PCs averaged 3 x 10(8) in RD PCs and ranged from 8.6 to 9.6 x 10(6) per SD PC. Residual WBC counts in filtered PCs ranged from 2.3 x 10(4) to 2.2 x 10(5) and those in WBC-reduced SD PCs averaged 2.2 x 10(5) per unit. The data demonstrate significant phenotypic differences among PCs produced with various procedures. All SD PCs and two of four filtered RD PCs contained five WBC populations including granulocytes and monocytes, while RD PCs filtered with the remaining manufacturer's devices contained only lymphocytes. CONCLUSION: The data confirm that distinct phenotypic differences exist among PCs prepared with different devices and/or procedures. It is suggested that as for non-generic pharmaceuticals, the clinical benefits of these various PCs should be individually proved.

Dual role of HIV Tat in regulation of apoptosis in T cells.

Apoptosis has been suggested to be one of the major mechanisms of depletion of CD4+ T cells in HIV-1-infected individuals. Remarkably, HIV-1-infected cells appear protected from apoptosis, whereas bystander cells show increased apoptosis in lymph nodes of infected individuals. In this work, we present evidence that the trans-activating protein of HIV-1, Tat, has a dual role in regulation of apoptosis in T cells. While addition of exogenous Tat protein induced apoptosis in uninfected T cells, T cell clones stably expressing the Tat protein were protected from activation-induced apoptosis. The addition of exogenous Tat potentiated anti-CD3 mAb, anti-Fas IgM mAb, and TNF-alpha-induced apoptosis of T cells. Pretreatment of Tat with anti-Tat Ab abrogated Tat-induced apoptosis, but did not affect anti-Fas IgM Ab-induced apoptosis. Endogenously expressed Tat was analyzed in Jurkat T cell clones transfected with either full-length tat gene (101 amino acids), or in control cells containing an empty vector. The Tat101-transfected clones were resistant to anti-CD3-induced apoptosis, when compared with cells transfected with vector alone. Furthermore, cross-linking of CD4 molecules on T cells with gp160 and anti-gp160 Ab showed markedly decreased apoptosis in Tat101 cells compared with that induced in cells transfected with vector alone. Taken together, our results indicate that HIV-1 Tat can regulate apoptosis that may contribute to the immunopathogenesis of AIDS.