Naturally occurring immunosuppressive agents. II. The ability of cell-free liver extracts to modify the rejection of allogeneic skin grafts in the rabbit.

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.

Naturally occurring immunosuppressive agents. I. The presence in normal pig liver of a factor possessing immunosuppressive properties with respect to pig lymphoid cells in vitro.

Saline cell-free extracts of normal pig liver, but not normal pig spleen, contain a noncytotoxic factor (or factors) capable of suppressing the blastogenic response of pig lymphocytes to stimulation with a number of plant mitogens: phytohemagglutinin, pokeweed, and concanavalin A. This reaction is generally considered to be a reflection of the capacity of the cell to participate in an immune reaction. Normal pig serum does not display inhibitory activity. The liver extract must be in contact with the lymphocytes for at least the final 48 hr of the 72-hr culture period in order to suppress the blastogenic response. Whether this active constituent in normal pig liver extract is an immunosuppressive agent in vivo remains to be determined.

Orthotopic liver transplantation utilizing a vascular stapling instrument.

A technique of orthotopic liver transplantation in the pig is described in which the main feature is the accomplishment of four of the five anastomoses by the use of the Vogelfanger NRC vascular suturing instrument. The advantage of this instrument is the rapid accomplishment of safe leak-proof anastomoses.