Progressive expansion of an L-selectin-negative CD8 cell with anti-feline immunodeficiency virus (FIV) suppressor function in the circulation of FIV-infected cats

The acute stage of feline immunodeficiency virus (FIV) infection is characterized by the appearance of a major CDS subpopulation with reduced expression of the CD8 beta chain (CD8 alpha(+)beta(lo)), CD8 antiviral activity was subsequently shown to be mediated by the CD8 alpha(+)beta(lo) phenotype, which is the dominant CD8 phenotype in long-term infected cats. Two- and three-color how cytometric analysis demonstrated that the CD8 alpha(+)beta(lo) subset is L-selectin negative (CD62L(-)) and has increased expression of CD44, CD49d, and CD18, consistent with an activation phenotype, The CD8 alpha(+)beta(lo)CD62L(-) cells but not the CD8 alpha(+)beta(hi)CD62L(+) cells demonstrated strong antiviral activity in the FIV acute-infection assay. The progressive expansion of the CD8 alpha(+)beta(lo)CD62L(-) effector subset cells in FIV-infected cats parallels that seen in human immunodeficiency virus (HIV)-infected patients, suggesting that failure in homeostatic mechanisms regulating lymphocyte activation or trafficking (or both) may be a consequence of both HIV and FIV infections.