Immunology
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Short-lived SAMP-P/1 mice are low responders in in vitro antibody responses because of a selectively impaired helper T(Th)-cell activity. After crossing with high responders (B10. BR mice), about 12% of (B10. ⋯ Low responders in the F2 generation showed a significantly higher incidence of SAM-P/1 genotype at the Gpi-1 as well as c locus on chromosome 7 (Chr.7). However, no linkage of low responsiveness to the Hbb locus was evident, an area present at a more distal site to the centromere on the same chromosome. These results suggest that one of the genes controlling the hypo-responsiveness of SAM-P/1 mice is linked to both Gpi-1 and c loci and that it locates at a more proximal site on Chr.7.