Not only can opioids potentiate the production of chemokines that are known mediators of HIV encephalitis, such as CCL5/RANTES and CCL2/MCP-1 [15-17], but opioid and chemokine systems can undergo mutual cross-desensitization [18,19], and opioid and chemokine receptors may interact directly at the molecular level through the formation of heterodimers [20-22]. Here, CCL2 is linked to AIDS dementia complex.