The Journal of immunology : official journal of the American Association of Immunologists
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We previously demonstrated that treatment of (C57BL/6 X A)F1 (F1) recipient mice with polyinosinic:polycytidylic acid (pI:C) before injection with 30 X 10(6) C57BL/6 (B6) lymphocytes prevents both the immunosuppression and pathologic lesions typical of graft-vs-host (GVH) reactions. We now report the further characterization of this phenomenon. Donor spleen and lymph node cells were labeled with fluorescein in vitro and injected into pI:C-treated or untreated mice. ⋯ The results show that this capacity was not blocked by 750 cGy, a dose of radiation that abrogates most T and B cell functions. Furthermore, rejection of parental cells could be prevented by treatment of recipient F1 mice with antibodies to asialo GM1, a treatment that suppresses NK activity. These data demonstrate that pI:C-mediated protection from GVH-induced changes is due to increased rejection of grafted B6 parental cells by F1 NK cells, a phenomenon very similar, if not identical, to HR to bone marrow grafts.