The effect of exposing murine splenocytes to UVB light, psoralen plus UVA light, or γ-irradiation on in vitro and in vivo immune responses

BACKGROUND: WBCs in blood components are a major factor contributing to immune responses such as GVHD and allommunization that follow transfusion. Irradiation of blood components has been used to regulate the contribution of donor WBCs to these immune responses. A systematic comparison of how the exposure of lymphoid cells to gamma-irradiation, UVB light, or psoralen + UVA light (PUVA) effects immune response was conducted to better define the best type of irradiation to be used in different clinical settings. STUDY DESIGN AND METHODS: Murine spleen cells were irradiated with varying doses and tested for their in vitro ability to be activated, to proliferate in response to mitogen or allogeneic stimulator cells, or to serve as stimulator cells. Irradiated donor cells were also tested for in vivo generation of GVHD, induction of alloantibody production, induction of restricted cytolytic T lymphocytes, and persistence of irradiated cells. RESULTS: In general, increasing amounts of irradiation resulted in increased inhibition of in vitro and in vivo responses, although the doses required for inhibition differed from assay to assay. In contrast, irradiation of donor cells did not always result in inhibition of recipient alloantibody responses but was dependent on the donor-recipient combination that was studied. CONCLUSION: Control of the in vivo outcomes of transfusing allogeneic cells is regulated by the type and dose of irradiation used and by the genotype of the donor and/or recipient.