The enhancement of polyclonal T cell proliferation by beta-endorphin

Beta-endorphin (beta-end) is a naturally occurring opioid peptide that has been implicated as a modulator of immune function. In this communication, data are presented to illustrate that beta-end enhances proliferation of murine splenocytes stimulated by the T cell mitogen, Con A. The T cell sensitivity of this effect was demonstrated in cell preparations enriched for T cells by nylon wool separation. The opioid specificity of the enhancement indicates that the C-terminus of the 31 amino acid peptide contributed significantly to the effect. In addition, the magnitude and the incidence of the enhancement was highly dependent on the concentration of Con A, the density of the tested cells and the timing of the addition of beta-end relative to that of Con A. These observations suggest that the state of activation of the T cell is a principal determinant of its sensitivity to beta-end. Overall, the data provide compelling evidence for the existence of an immunomodulatory role for beta-end.