It has been recently reported that the nervous and immune systems can influence each other in a variety of wa. The effect of opioids on defense mechanisms is of particular interest because drug addicts are prone to infectious diseases such as HIV-1, and morphine and its derivatives may serve as cofactors in the spreading of the diseases. We are interested in studying how macrophages are affected by opioids, because these cells play a pivotal role in cellular defense, and in moderating the generation of antibodifies. We have demonstrated in our laboratory that morphine and other opioids can affect phagocytosis and nitric oxide production in murine macrophasges. We have also demonstrated that when these sells are chronically exposed to morphine, phagocytosi is no longer affected suggesting the induction of a state to desentization or tolerance. We plan to study these effects further by conducting a detailed pharmacological study to determine if true morphine tolerance4. We plan to study these effects further by conducting a detailed pharmacological study to determine opiod receptor involved in these effects.