| Abstract: | The response by the mother to the paternal antigens of her foetus was evaluated in the rat by the production of a serum factor which inhibits macrophage migration (serum inhibitory factor, SIF). The SIF response depended upon antigenic differences controlled by genes within the major histocompatibility complex (MHC), as demonstrated by the use of congenic strains. Differences between mother and foetus within the RT1.A* region of the MHC led to SIF stimulation, whereas, differences in the RT1.B region did not. The SIF response followed the course of the pregnancy: it began at the time of implantation, reached a maximum at birth and then fell precipitously. In contrast, the SIF response to skin grafting did not correlate with differences in the MHC. Thus, the antigenic factors stimulating this maternal response to foetal antigens appear to depend upon a unique type of genetic difference, and this may be a factor in the apparent immunologic privilege enjoyed by the foetus during gestation. |
