Spontaneous T-cell apoptosis in feline immunodeficiency virus (FIV)-infected cats is blocked by the addition of IL-2 and anti-B7.1 antibodies

Bull, M. E.; Vahlenkamp, Thomas W. GND; Dow, J. L.; Collisson, E. W.; Winslow, B. J.; Tompkins, M. B.; Tompkins, W. A.

Lymph node (LN) T cells from feline immunodeficiency virus (FIV)-infected cats have an increased expression of B7 co-stimulatory molecules as well as their ligand CTLA4, resembling an activation phenotype shown to induce anergy and apoptosis in activated T cells. In addition, LN T cells from FIV-infected cats also show increased spontaneous apoptosis compared to uninfected animals. The apoptosis observed in these animals occurs primarily in T cells expressing B7 and CTLA4, suggesting a role for B7 and CTLA4 interactions in the induction of anergy/apoptosis. In order to investigate the role of B7 and CTLA4 interactions on T cell apoptosis in LN T cells from FIV-infected cats, we performed blocking experiments by measuring T cell apoptosis in LN T cell cultures treated with anti-feline B7.1, B7.2, and CTLA4 specific antibodies, as well as interleukin (IL)-2. The addition of IL2, the primary cytokine produced by B7/CD28 interactions, resulted in a significant decrease of T cell apoptosis in cultured LN cells as assessed by two-color flow cytometry and TUNEL assay. The addition of anti-B7.1 antibodies significantly inhibited T cell apoptosis in FIV-infected cats with low-level plasma viremia, while addition of anti-B7.2 and anti-CTLA4 antibodies had no affect. These results suggest a role of B7 signaling in the increased spontaneous apoptosis observed in LN T cells from FIV-infected animals.

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Bull, M. E. / Vahlenkamp, Thomas W. / Dow, J. L. / et al: Spontaneous T-cell apoptosis in feline immunodeficiency virus (FIV)-infected cats is blocked by the addition of IL-2 and anti-B7.1 antibodies. 2004.

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