Evidence that specific cellular immunity cannot account for death of Mus caroli embryos transferred to Mus musculus with severe combined immune deficiency disease.

Mus caroli blastocysts transferred to pseudopregnant Mus musculus implant but die about midgestation. Death of the M caroli embryos is associated with infiltration of the fetoplacental units by M musculus lymphocytes, including functional cytotoxic T lymphocytes (CTL). To determine if specific maternal antifetal immune responses are responsible for the initiation of M caroli failure, survival of M caroli embryos transferred to M musculus with severe combined immune deficiency disease (SCID) was studied. C.B.-17 scid mice, homozygous for the scid gene, are reported to be unresponsive to T cell or B cell mitogens and to alloantigens. We have evaluated responses of C.B.-17 scid mice to M caroli xenoantigens in vivo and in vitro. C.B.-17 scid fail to reject M caroli skin grafts, and their spleen cells do not proliferate when mixed with M caroli splenocytes in a 1-way mixed leukocyte culture. Further, neither primary nor secondary challenge of C.B.-17 scid footpads with M caroli splenocytes elicits a delayed-type hypersensitivity (DTH) response. These results suggest that C.B.-17 scid mice are unable to recognize or respond specifically to M caroli xenoantigens. M caroli embryos transferred to C.B.-17 scid mice implant but fail to survive while cotransferred M musculus embryos are normal. Histologic examination of resorbing embryos revealed granulocytes, macrophages, large granular lymphocytes, but very few small lymphocytes at the implantation sites. Thus, it appears that specific maternal antifetal immune responses are not responsible for initiation of M caroli embryo failure in the M musculus uterus. These studies also indicate that efficient resorption of embryos does not require the function of T cells or B cells.