Effect of proline-rich polypeptide on donor cells in graft-versus-host reaction

The effect of a proline-rich polypeptide (PRP) isolated from early sheep colostrum on the graft-versus-host (GvH) reaction was studied. Unfractionated thymocytes, treated with PRP in vivo or in vitro, acquired the ability to elicit the GvH reaction. In fact PRP elicited GvH reactivity in cortisone-sensitive thymocytes and cortisone-sensitive thymocytes become cortisone-resistant after incubation with PRP. On the other hand, some of the cortisone-resistant thymocytes become cortisone-sensitive when treated with PRP and the ability to induce the GvH reaction was reduced.