INCREASED EXPRESSION OF CD80, CD86 AND CD70 ON T-CELLS FROM HIV-INFECTED INDIVIDUALS UPON ACTIVATION IN-VITRO - REGULATION BY CD4(-CELLS() T)

T cells express CD28 and CD27 which transduce co-stimulatory signals a fter interaction with their ligands on antigen-presenting cells (APC). These ligands, CD80, CD86 and CD70, are also expressed to some extent on activated T cells. Here, we show that in human immunodeficiency vi rus (HIV)-infected individuals, CD28 and CD27 expression is decreased on CD8(+) T cells. On the other hand, T cell stimulation in vitro indu ced high CD80, CD86 and CD70 expression on T cells from HIV-infected i ndividuals. It appeared that an inverted CD4:CD8 T cell ratio could ex plain this enhanced expression of co-stimulatory ligands. Indeed, high expression levels of CD80, CD86 and CD70 were found on activated CD8( +) T cells from HIV- individuals cultured in the absence of CD4(+) T c ells. Addition of CD4(+) T cells prevented this up-regulation. However , in HIV-infected individuals, addition of excess autologous or health y control CD4(+) T cells did not completely counteract up-regulation o f co-stimulatory ligand expression on CD8(+) T cells. Thus, to some ex tent, CD8(+) T cells in HIV-infected individuals appeared to be refrac tory to CD4(+) T cell-mediated regulation of ligand expression in vitr o. Activated T cells from HIV-infected individuals and activated CD8() T cells from healthy controls were able to act as accessory cells in CD3-induced T cell proliferation, which was dependent on cell-cell co ntact. Thus, we showed that T cells from HIV-infected individuals expr ess enhanced levels of co-stimulatory ligands upon activation, which p rovides them with accessory cell properties. Enhanced stimulatory pote ntial of these nonprofessional APC may contribute to persistently high levels of immune activation in HIV infection related to disease progr ession.