Detection of opioid receptors on murine lymphocytes by indirect immunofluorescence: mature normal and tumor bearing mice lymphocytes.

Opioid peptides modulate immune responses via ligation to classical opioid receptors (mu, delta and kappa), expressed on immune cells, or in an indirect fashion via the central nervous system. The combination of immunofluorescent technique and flow cytometry has proven to be sensitive methods for detection of opioid receptors on leukocytes. In the current study a fluorescein isothiocyanate-conjugated naltrexone (FITC-NTX) derivative in the absence or presence of naltrexone, as a competitor, was used to detect opioid receptors on thymocytes and then on splenocytes of normal and tumor bearing Balb/c mice.