Minor Antigen Disparities Impede Induction of Long Lasting Chimerism and Tolerance through Bone Marrow Transplantation with Costimulation Blockade

Figure 2

mHAg are a barrier for induction of donor specific tolerance through BMT plus CB. (a) BL6 () recipients of bone marrow of fully MHC mismatched Balb/c (, mHAg mismatched), B10.D2 (), or B10.A (, both mHAg matched) mice were tested for donor specific tolerance through transplantation of donor type and 3rd party skin 7 or 14 weeks after BMT. Treatment with 3 Gy TBI (): transplantation of BMC together with CB (1 mg anti-CD154mAb, d0; 0.5 mg CTLA4Ig, d2) leads to long lasting (>130 days) donor skin graft acceptance in long-term chimeras, which had received BMC from MHC and mHAg mismatched Balb/c () donors in 10 of 13 mice. Significantly better graft survival was observed in long-term chimeric recipients of MHC mismatched but mHAg identical bone marrow (28/29, B10.D2 and B10.A, ; pooled data from 2 independent experiments). Skin graft survival was calculated according to the Kaplan-Meier product limit method and compared by using the log-rank test. versus Balb/c donors. (b) Chimerism levels of long-term chimeras, which received Balb/c BMC were not significantly different in tolerant mice (circles ○) compared to mice, which rejected (squares ■) donor skin grafts. = n.s. for all time points. (c) Macroscopical aspects of Balb/c (, mHAg mismatched) donor skin grafts changed during the observation period with grafts showing shrinking, thickening, and loss of surface structure. In comparison, donor grafts of B10.D2 () and B10.A (, both mHAg matched) mice stayed macroscopically unchanged from 7 days after skin grafting (when protecting bandage was removed) until the end of observation period. (d) Representative histology of donor skin grafts of Balb/c (left), B10.D2 (middle), and B10.A (right) 44 weeks after skin grafting. HE staining, magnification 160x, and Giemsa staining 160x (not shown) analyzed. (e) Classification of donor skin grafts 44 weeks after skin grafting according to The Banff 2007 Working Classification of Skin-Containing Composite Tissue Allograft Pathology [19] by a blinded expert pathologist. versus Balb/c. Most of Balb/c donor skin grafts showed histologically moderate (grade 2, 2/3) signs of inflammation whereas all B10.D2 donor skin grafts were free of inflammatory infiltrates (grade 0, , ). B10.A partially showed no (grade 0, 2/4) or mild signs of inflammation (grade 1, 2/4, n.s. versus Balb/c).

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