Enhanced expression of novel CD57+CD8+ LAK cells from cats infected with feline immunodeficiency virus.

As a model for lymphokine-activated killer (LAK) function in HIV infection, we studied LAK cells in cats infected with feline immunodeficiency virus (FIV), which causes an acquired immunodeficiency syndrome. Peripheral blood mononuclear cells cultured in concanavalin A and interleukin-2 developed LAK cytotoxicity against chronically FIV-infected CrFK cells and acutely infected CD4+ lymphocytes but not uninfected cells. LAK cells from FIV+ cats were more cytotoxic than LAK cells from uninfected cats. Enhanced FIV+ LAK cytotoxicity against feline leukemia virus-infected cells (FL74) suggested that the cytotoxicity was not antigen specific. Two-color fluorescence-activated cell sorter analysis and antibody depletion studies demonstrated that the majority of LAK cells and their progenitors were positive for both CD8 and CD57. The in vitro induction of dual positive CD8+CD57+ LAK cells was enhanced in FIV+ cats, as reported for HIV+ patients. These CD8+CD57+ LAK cells may play a role in maintaining the long asymptomatic stage of infection in FIV+ cats.