The initial idea that exogenous opiates can affect immune function was first floated in 1898 when Cantacuze described the effect of opium on leukocyte phagocytosis in guinea pig model. Recently findings from several investigators (Quaglio et al., 2002; Nath et al., 2002; Georges et al., 1999; Vallejo et al., 2004; Roy et al., 2006; Somaini et al., 2008) support the role of opiates in suppressing a variety of immunological end points in opiate abusers. Endogenous opioids seem to have a physiological role in modulating the Th1/Th2 balance, by reducing Th1 and enhancing Th2 representative cytokines. Exogenous opioids, on the other.
