CD8+ T Lymphocytes Can Amount a Second-Set Rejection of Skin Allografts in the Absence of Cytotoxic Antibodies

Second-set rejection of organ or skin allografts is usually considered to result from humoral immunization. Because the correlation between such accelerated rejections and cytotoxic antibodies shows discrepancies, we have investigated the occurrence of rejection in mice without anti-H2 antibodies but with normal cellular immunity. Two models were used: (a) chimeric mice, and (b) agammaglobulinemic, T-cell reconstituted RAG mice. Transplantation of 20 × 106 fetal liver cells from Balb/c (H-2D) mice to lethally irradiated CBA (H-2k) mice resulted in construction of (Balb/c CBA) chimeras. Following hyperimmunization with third party B6 (H-2b) skin transplants and with 3 injections of 2 × 107 B6 spleen cells, antibody production and skin graft survival were analyzed. Anti-B6 cytotoxic antibodies were not detectable in any of hyperimmunized chimeric mice, yet accelerated rejection of B6 transplant occurred: graft survival of 8.6 ± 0.5 days (d), comparable to the 8.9 ± 0.8 d survival in CBA control mice subjected to the same hyperimmunization procedure, and significantly shorter than in non-hypermmunized (Balb/c CBA) chimeras (11.6 ± 0.5 d) or in non-hyperimmunized CBA control mice (12.1 ± 0.6 d). High titers of anti-B6 cytotoxic antibodies were present in the serum of hyperimmunized CBA control mice. To further analyze the factors or cells responsible for accelerated rejection in hyperimmunized chimeras, transfer experiments carried out, involving the injection of serum, whole spleen cells, spleen T cells, spleen CD8+ T cells or spleen CD4+ T cells from chimeras into Balb/c mice that had received 600 cGy irradiation. The recipient mice were then grafted with B6 skin. The graft survival was over 14 d in mice treated by irradiation only or by irradiation + serum or + CD4+ T cells. It was significantly shorter in mice treated by irradiation +whole spleen cells or + T cells (9.0 ± 0.7 d) or + CD8+ T cells (9.5 ± 0.6 d).