• Tsuyoshi Todo, Gordon Wu, Ning-ning Chai, Yao He, Gislaine Martins, Ankur Gupta, Jeffrey Fair, Nai-you Liu, Stanley Jordan, and Andrew Klein.
• Comprehensive Transplant Center and Department of Surgery, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.
• Int. Immunol. 2012 Aug 1; 24 (8): 529-38.

AbstractAntibodies targeting T cells and B cells are increasingly used for immunosuppression in clinical transplantation. However, the impact of T-cell depletion by antibodies on B-cell homeostasis is poorly understood. Using a mouse model of allosensitization with skin allograft, we investigated whether targeting T cells by anti-CD3ε alters peripheral B-cell homeostasis and alloantibody responses following B-cell depletion by anti-CD20. We found that anti-CD3ε induced a discrete B220(lo), but not a conventional B220(hi) subset, in the spleens of the allosensitized mice 14 days after anti-CD20 treatment. The splenic B220(lo) cells were refractory to anti-CD20 depletion. Flow cytometry revealed that the splenic B220(lo) cells were phenotypically similar to the B220(lo) AA4.1(+) CD23(-) sIgM(lo) sIgD(-) developing B cells (pre-B to immature B) normally presented in the bone marrow. Despite the presence of the splenic B220(lo) cells, mice treated with combined anti-CD3ε/CD20 produced limited alloantibodies in response to the primary skin allografts. Alloantibody production increased significantly in the mice following re-immunization by donor-specific splenocytes. We conclude that anti-CD3ε can induce an expansion of B220(lo) B cells in the spleens after B-cell depletion by anti-CD20. These B cells are not producing alloantibodies, but re-immunization of the mice with alloantigen leads to risk of alloantibody response.

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