ACUTE EXPOSURE TO MORPHINE SUPPRESSES CYTOTOXIC T-LYMPHOCYTE ACTIVITY

Chronic exposure (11 days) to morphine has previously been shown to su ppress splenic and peritoneal cytotoxic T-lymphocyte activity through mu-opioid receptors. The present study was undertaken to assess the ef fects of varying the frequency of exposure to morphine on cytotoxic T- lymphocyte activity in C3H/HeN mice immunized with C57BL/6 splenocytes . Mice subchronically treated with morphine (50.0 mg/kg) showed no mea surable suppression of splenic natural killer activity or splenic or p eritoneal cytotoxic T-lymphocyte activity. However, mice treated acute ly with 50.0 mg/kg of morphine exhibited a significant suppression of peritoneal but not splenic cytotoxic T-lymphocyte activity. Naltrexone pretreatment of mice receiving an acute dose of morphine blocked the suppression, implicating the involvement of opioid receptors. Using co lumn depletion chromatography, peritoneal exudate cells mediating cyto toxic T-lymphocyte activity were both CD4(+)CD8(-) and CD4(-)CD8(+). C ollectively, the results suggest that the duration of opioid (morphine ) exposure differentially affects peritoneal cytotoxic T-lymphocyte ac tivity. These results may have important implications regarding immuni ty to viral infections in individuals who abuse drugs such as heroin.