Microchimerism maintains deletion of the donor cell–specific CD8+ T cell repertoire
Weldy V. Bonilla, Markus B. Geuking, Peter Aichele, Burkhard Ludewig, Hans Hengartner, Rolf M. Zinkernagel
Weldy V. Bonilla, Markus B. Geuking, Peter Aichele, Burkhard Ludewig, Hans Hengartner, Rolf M. Zinkernagel
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Research Article Immunology

Microchimerism maintains deletion of the donor cell–specific CD8+ T cell repertoire

Abstract

Rare cases of stable allograft acceptance after discontinuation of immunosuppression are often accompanied by macrochimerism (> 1% donor cells in blood) or microchimerism (< 1% donor cells in blood). Here, we have investigated whether persistence of donor cells is the cause or the consequence of long-lasting CTL unresponsiveness. We found that engraftment of splenocytes bearing a single foreign MHC class I–restricted epitope resulted in lifelong donor cell microchimerism and specific CTL unresponsiveness. This status was reversed in a strictly time- and thymus-dependent fashion when the engrafted cells were experimentally removed. The results presented herein show that microchimerism actively maintains CTL unresponsiveness toward a minor histocompatibility antigen by deleting the specific repertoire and thus excluding dominant, T cell extrinsic mechanisms of CTL unresponsiveness independent of systemically persisting donor cell antigen.

Authors

Weldy V. Bonilla, Markus B. Geuking, Peter Aichele, Burkhard Ludewig, Hans Hengartner, Rolf M. Zinkernagel

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Figure 3

Protocol used for termination of chimerism by adoptive transfer of LCMV-specific CTLs.

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Protocol used for termination of chimerism by adoptive transfer of LCMV-...
(A) Euthymic (B6) or thymectomized (B6TX) mice (black) were transfused with sex-matched H8 splenocytes (blue). This resulted in permanent mixed chimerism, represented by endogenous (black) and donor (blue) cells. Either 28 or 700 days later, recipients were additionally transfused with splenocytes from B6 × BALB/b F1 mice that had been infected with LCMV 10 days previously (red, d10-LCMV-F1). GP33-specific d10-LCMV-F1 CTLs eliminated H8 donor cells in an H-2Db-restricted manner. BALB/b miH epitopes expressed by the transferred cells elicited a BALB/b-specific response, rejecting the transferred d10-LCMV-F1 cells within 7 days. At different time points after transfer of d10-LCMV-F1 cells, recipients were challenged with LCMV, and endogenous GP33-specific and NP396-specific CTL responses were measured 8 days later. (B) B6 recipients of CFSE-labeled H8 splenocytes were transfused i.v. with d10-LCMV-F1 (B6 × BALB/b) splenocytes (open diamonds) or were left untreated (filled circles). The percentage CFSE-positive lymphocytes in blood was determined by flow cytometry. Symbols represent the mean ± SD of 3 mice. (C) DNA from blood of H8 donor cell recipients was isolated before (day 23) and after (day 57) transfer of d10-LCMV-F1 cells on day 28 and from control H8 donor cell recipients without d10-LCMV-F1 transfer for H8-specific PCR analysis. (D) CFSE-labeled d10-LCMV-F1 (B6 × BALB/b) (filled triangles) or control B6 splenocytes (filled diamonds) were adoptively transferred to sex-matched B6 recipients, and the percentage of CFSE-positive lymphocytes in blood was determined by flow cytometry. Symbols represent the mean ± SD of 4 mice. One representative experiment of 3 (B and C) or 2 (D) is shown.