Background: The ORL-1 receptor is expressed by human leukocytes. Limited knowledge exists about the function and interaction between the nervous and immune systems. The aim of our study was to investigate the expression of the nociceptin-ORL-1 receptor system on different leukocyte subsets and the influence of the ORL-1 receptor on the intracellular production of cytokines.
Methods: Blood from healthy volunteers of different age and sex was analysed for the expression of the ORL-1 receptor by PCR and flow cytometry and the influence of nociceptin on the LPS-induced production of intracellular cytokines by flow cytometry.
Results: The ORL-1 receptor mRNA is expressed by granulocytes, lymphocytes and monocytes. We could also show the expression of the ORL-1 receptor protein on the cell surface of all types of white blood cells. Nociceptin has no influence on LPS-induced cytokine production in human monocytes. There was neither a difference between young and old nor between male or female volunteers.
Conclusion: The ORL-1 receptor is expressed by all subtypes of leukocytes. The function of this receptor is not the modulation of cytokine production and requires further studies.