Figure 3

Reduced natural tolerance to increasingly mismatched internal transplants lacking passenger lymphocytes; requirements for systemic chimerism. (A) Top survival graph, 1^st transplant: Graft survival in days post fetal liver injection is shown for STZ induced diabetic BALB/c-SCID mice that received B10.D2 WT vs. B10.D2-RAG islets (n = 11 and 14 respectively; p = 0.009) or B6-RAG islets (n = 10; p = 0.01 vs. B10.D2-RAG) 4–7 months pre-FL; control syngeneic BALB/c islets (not shown) survived long-term post FL reconstitution (>131, >185 × 3 days). Also shown is graft survival in days post islet transplant of B10.D2 WT islets (n = 7) given >13 weeks post-FL (thick grey line). Some recipients with functioning grafts beyond 100 days were given a 2^nd donor islet transplant (lower survival graph; B10.D2 WT, n = 8, vs. B10.D2 RAG, n = 3, p = 0.011; B6 RAG, n = 5). (B) Representative flow cytometry analyzing the presence and phenotype of donor cells from the PBL of mice shown in (A). T cells of the donor (Ly9.1^-) are present in recipients of WT but not RAG islets (lower right vs. left dot plots respectively). All 11 recipients were T cell chimeras, with 3.2 ± 1.6% of T cells being of donor origin (Ly9.1^- TCR⁺) in 7 mice analyzed at 30 weeks post FL injection. (C) Frequency of donor reactive (Vβ6) and control (Vβ8) T cells in the thymus (gated on host CD4 SP cells), spleen and blood (gated on host TCR⁺ cells) of normal BALB/c and DBA/2 mice, and BALB/c-SCID mice given BALB/c FL alone or DBA/2 islets before or after the FL (analysis at >33 wks after FL injection; mean ± SE; n = 2–5 mice per group). DBA/2 islets given after FL were rejected ~4 days prior to the Vβ analysis. Chimerism with islet-derived donor T cells (CD5.1⁺) in the spleen of the recipients with islets given pre-FL ranged from 1.4–3.9% of all T cells. Percent Vβ6 comparing SCID FL vs. SCID islets FL: p < 0.001 for thymus, blood, and spleen; comparing SCID islets FL to SCID FL islets: thymus, p > 0.05, spleen and blood, p < 0.001.