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Modulation of the in vitro murine immune response by met-enkephalin
R R Rowland1, R Chukwuocha, S Tokuda
1Department of Microbiology, School of Medicine, University of New Mexico, Albuquerque 87131.
Abstract:
The in vitro priming of mouse spleen cultures with sheep erythrocytes (SE) was used to study the modulation of immune function by met-enkephalin (MENK). In these studies, suboptimal, optimal, and supraoptimal concentrations of SE were used to manipulate the plaque-forming cell (PFC) responses of cultured spleen cells. MENK, at a concentration of 10(-7) M, was able to abolish the high antigen dose-induced suppression of the PFC response, but was unable to increase the PFC response of cultures treated with suboptimal doses of antigen. On rare occasions when the supraoptimal dose of antigen did not suppress the immune response, the addition of 10(-7) M MENK to the culture medium suppressed the PFC response. Naloxone was unable to block the effect of MENK. These results indicate that the nature of the immune response must be taken into consideration when evaluating the effect of opioid peptides on immune function. We propose that MENK possesses a dual modulatory role, with the abilities to suppress a strong immune response and reverse high antigen-induced immunosuppression.
Insights
Met-enkephalin (MENK) modulates immune responses by reversing high antigen-induced immunosuppression in mouse spleen cultures. However, MENK does not enhance responses to suboptimal antigen doses and can suppress strong immune reactions.
Area of Science:
- Immunology
- Neuroscience
- Pharmacology
Background:
- Opioid peptides, such as met-enkephalin (MENK), are known to influence immune cell function.
- The precise mechanisms and dose-dependent effects of MENK on immune responses require further elucidation.
Purpose of the Study:
- To investigate the immunomodulatory effects of met-enkephalin (MENK) on mouse spleen cell cultures.
- To determine if MENK can reverse immunosuppression induced by high antigen doses.
- To explore the dual role of MENK in modulating immune responses.
Main Methods:
- In vitro culture of mouse spleen cells.
- Priming with varying concentrations of sheep erythrocytes (SE) to induce immune responses.
- Treatment with met-enkephalin (MENK) at 10(-7) M.
- Assessment of plaque-forming cell (PFC) responses.
- Use of naloxone to investigate opioid receptor involvement.
Main Results:
- MENK (10(-7) M) reversed immunosuppression caused by supraoptimal antigen doses.
- MENK did not enhance immune responses to suboptimal antigen doses.
- MENK exhibited a suppressive effect on PFC responses when the immune response was not already suppressed.
- Naloxone did not block the observed effects of MENK.
Conclusions:
- Met-enkephalin (MENK) exhibits a dual role in immune modulation: suppressing strong responses and reversing high antigen-induced immunosuppression.
- The effect of MENK on immune function is dependent on the nature and strength of the immune response.
- Opioid peptide modulation of immunity is complex and context-dependent, not solely mediated by classical opioid receptors.