Dominant suppressive effect of the silent Eαb allele on anin vivo T helper cell response under Eβd Eαd region-linked immune response gene control

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Abstract
Previous adoptive spleen cell transfer experiments have demonstrated that an immune response (Ir) gene linked to the E E region allows BALB/c T helper lymphocytes (Th) to respond to an idiotope on the Vλ2315 fragment of isologous myeloma protein M315. BALB.K (H-2k) and BALB.B (H-2b) do not respond to Vλ2315. While (H-2d × H-2k)F1 hybrids have been shown to be responders, it is now demonstrated that (H-2d × H-2b)F1 hybrids are low responders. By crossing BALB/c with various H-2 recombinants on B10 background and probing Th responsiveness to Vλ2315 in these F1 hybrids, the dominant suppressive gene of the H-2b haplotype is mapped to E Sb. It is argued that the suppressive gene is E, which is a silent allele. A likely explanation for the suppressive effect of the E allele is that reduced amounts of E: E restriction elements are present on antigen-presenting cells of (H-2d × H-2b)F1hybrids because only one Ea gene is functional in such mice. The present report extends previous in vitro findings from other laboratories to the in vivo situation and suggests that silent alleles for class II molecule chains may profoundly affect certain immune responses of individuals heterozygous for the silent allele.

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