Naturally Occurring Immunosuppressive Agents II. The Ability of Cell-Free Liver Extracts to Modify the Rejection of Allogeneic Skin Grafts in the Rabbit

Abstract

It has been demonstrated that cell-free extracts of pig, rabbit and human liver, but not of other parenchymal organs, contain a factor or factors capable of suppressing the proliferative responses of allogeneic and xenogeneic lymphoid cells stimulated with PHA, PWM, Con-A and allogeneic lymphocytes. Intravenous injection of the liver extract is capable of modifying significantly the skin allograft rejection reaction in normal adult outbred rabbits. Work is now in progress to isolate this factor and to determine its composition.

Characterization of Murine Liver‐Derived Inhibitory Protein

“…dogs [4]. pigs [26], rabbits [27], and mice [ 1 ]. This factor was termed liver-derived inhibitory protein (LIP) by Schumacher cf a/, [21], and is capable of inhibiting the proliferation of both T and B lymphocytes in a dose-related manner [22].Grol & Schumacher have purified LIP from human liver [10], while our laboratory has purified it from miceliver [28].…”