Immunostimulating activity of synthetic bursopeptides.

Biologically active peptides bursopeptide-1 (Tyr-Glu-Glu) and bursopeptide-2 (Trp-Thr-Ala-Glu-Glu-Lys-Gln-Leu) from the bursa of Fabricius were isolated and synthesized. Bursopeptide-1 stimulated expression of B cell differentiation antigens in lymphocyte culture from patients with burns. Bursopeptide-2 produced a variety of effects and stimulated expression of differentiation antigens on T and B cells and natural killer cells. Bursopeptides can modulate the mechanisms of interleukin-2-mediated lymphocyte activation. Bursopeptides stimulated the immune response in mice with cyclophosphamide-induced immunodeficiency, which manifested in increased hemagglutinin and hemolysin titers and increased count of antibody-producing cells in the spleen.