Colostrinine: a proline-rich polypeptide from ovine colostrum is a modest cytokine inducer in human leukocytes.

A proline-rich polypeptide (PRP), now named colostrinine, molecular weight 18,000, was isolated from ovine colostrum and characterized by Janusz, Lisowski et al. The nonapeptide (NP) which is an active fragment of PRP was obtained by chemical synthesis. In mice, PRP has many regulatory effects on the humoral and cellular immune response. The present paper describes PRP as a cytokine inducer. PRP at concentration of 1-100 micrograms/ml was found to induce production of interferon (IFN) and tumor necrosis factor (TNF) in human peripheral blood leukocytes and in whole blood cultures. The effects were dose related. The identified till now cytokines induced by PRP were IFN-gamma and TNF-alpha but many other cytokines may be stimulated also. NP was considerably less active as the cytokine inducer than the natural PRP. Two volunteers given orally once daily for two to three weeks 100 or 200 micrograms PRP in tablets were found to develop the tolerance of IFN induction and had the modified TNF response. Furthermore, the PRP-treated volunteers showed signs of psycho-stimulation. Taken together our observations suggest that ovine PRP is active in humans and may have therapeutic value as an immunostimulant and/or neurotropic cytokine.