Test of prolongation of skin graft survival by blood injections provides evidence for presence of a new histocompatibility locus in the B-G region of chicken MHC.

When used for pretransplantation treatment, blood of congenic chicken lines CB and CB.R1, incompatible only in the B-G region of the major histocompatibility complex (MHC), differed in their ability to induce prolonged survival of skin grafts transferred from either of these lines onto recipients of a third congenic line, CC. Moreover, skin grafts from CB and CB.R1 donors displayed a difference in survival time, irrespective of blood pretreatment. Graft survival time after pretreatment of recipients with CB blood could be prolonged by prior induction of neonatal tolerance to the B-G product; this could be done with injections of whole blood or of separated erythrocytes or leucocytes of line CC.R1 chickens (incompatible with CC recipients in the B-G region). The results indicate that a new histocompatibility locus is present in the B-G region of the chicken MHC.