Certain host-donor strain combinations do not reject brain allografts after systemic sensitization

To investigate the factors related to allogenic brain graft rejection, rat cortex from either LEW-RT1l or BN-RT1n rats was transplanted into brains of several isogenic and allogenic inbred strains: F344-RT1l, LEW-RT1l, BN-RT1n, AO-RT1u, PVG-RT1c, PVG-RT1u, and PVG-RT1l. Each donor and host combination was subsequently subdivided into two subgroups. One group was systematically sensitized twice with donor skin tissue and another group served as a sham-sensitization control. Four weeks after the second sensitization, host brains were examined histologically, and the percentage volume of each graft that showed increased cellularity was estimated. Expression of major histocompatibility complex (MHC) and T cell antigens was also studied immunocytochemically. Almost all grafts in sham-sensitized animals from all groups were accepted with minimal or no reaction. However, two strains (AO-RT1u and F344-RT1l) showed considerable cell infiltration and expression of MHC antigens even without sensitization. After sensitization, almost all allogenic strain combinations showed greater signs of rejection-related responses. The severity of the tissue reaction, however, varied considerably between groups. All grafts from BN-RT1n donors were rejected severely in all host strains. For LEW-RT1l donors, grafts survived well in some host strains (BN-RT1n, AO-RT1u, PVG-RT1c, and PVG-RT1u), even with MHC + non-MHC disparity. Curiously, F344-RT1l hosts rejected LEW-RT1l grafts even though the two strains have the same MHC loci, but different minor histocompatibility (mH) loci. For both donor strains, experimental autoimmune encephalomyelitis-susceptible hosts tended to show more vigorous rejection responses.(ABSTRACT TRUNCATED AT 250 WORDS)