GAMMA-DELTA T-CELLS IN RHESUS-MONKEYS AND THEIR RESPONSE TO SIMIAN IMMUNODEFICIENCY VIRUS (SIV) INFECTION

Recent reports of the increase in peripheral blood gamma delta T cells in HIV+ patients prompted us to examine the gamma delta T cell system in rhesus monkeys (Macaca mulatta) and the responses of these cells t o SIV infection. Our results reveal differences in the gamma delta T c ell subset composition and their expression of CD8 in the peripheral b lood of monkeys and humans. The outgrowth of simian gamma delta T cell s in response to Daudi cells is similar to that in humans, but the exp osure to IL-2 stimulates preferentially the simian V delta 1 subset ra ther than the V gamma 9/V delta 2 subset as found in humans. Upon SIV infection of the monkeys, we observed a transient increase of the perc entage of total gamma delta T cell and the V gamma 9 subset. gamma del ta T cells from infected animals also express more activation markers such as CD69, CD44 and the memory marker CD45RO. However, they respond to a lesser degree to Daudi or IL-2 stimulation in the outgrowth expe riments compared with uninfected animals, although the subset composit ion of total gamma delta T cells is similar in infected and uninfected animals. The results clearly indicate that gamma delta T cells in rhe sus monkeys are influenced by SIV infection. The detailed analysis of the gamma delta T cell response to SIV infection can serve as a model for understanding human gamma delta T cell responses to HIV infections .