Influence of Myelopeptides on IL-1 and IL-2 Activities.

Myelopeptides are immunoregulatory molecules originally isolated from porcine bone marrow cell culture. The influence of synthetic analogous of these peptides on IL-1 and IL-2 activities was studied. Myelopeptide-1 but not myelopeptide-2 replaced IL-1 activity in a test of costimulation of thymocyte proliferation in the presence of mitogen. Conversely, myelopeptide-2, but not myelopeptide-1, stimulated both production of IL-2 by murine splenocytes and IL-2-dependent proliferation of CTLL-2 cell line. The enhancing effect of myelopeptide-2 on IL-2-associated processes was the most pronounced at the early stages of cell activation. The resting T cells stimulated with suboptimum doses of concanavalin A and activated T cells, expressing low level of IL-2R, were sensitive to myelopeptide-2 action. The possible role of myelopeptides in differentiation of T0 helper into T1 helper and T2 helper is discussed.

Participation by opioids in the immunostimulatory activity of myelopeptides.

Bone marrow myelopeptides (MP), besides having immunostimulatory activity, had a pronounced dose-dependent effect on the development of pain sensitivity in mice. Nanogram amounts of MP evoked a hyperalgesic response and increased antibody formation to sheep red blood cells three to nine times. Milligram amounts of MP had a hypoalgesic effect and did not affect antibody response. Opioid peptides derived from the bone marrow MP are involved in the expression of the antibody response, and a mixture of synthetic opioids, corresponding in composition to that found in natural MP, stimulated antibody production. The antibody-stimulating effect of MP was abolished by naloxone. Of the opioid peptides, only beta-endorphin showed antibody-stimulating activity. On reversed-phase chromatography the antibody-stimulating peptides and beta-endorphin were eluted in different fractions, indicating that the immunostimulatory and opioid activities are produced by different peptide molecules.