Partial overlap of Ir gene-controlled responses to two proteins of limited relatedness: hen egg-white lysozyme and human lysozyme.

The plaque-forming cell (PFC) response to human lysozyme (HUL) is regulated by an Ir gene(s) located within the major histocompatibility complex of the mouse. Mice of H-2a, H-2k, H-2v and H-2r haplotypes respond to HUL, whereas mice with H-2b, H-2d, H-2q, H-2s and H-2u haplotypes fail to generate substantial anti-HUL PFC responses. In contrast, only mice carrying the H-2b and H-2s haplotypes are non-responders to the distantly related hen eggwhite lysozyme (HEL). The major genetic control of the anti-HUL PFC response maps to the I-A subregion of the H-2 complex with perhaps a minor influence by a gene mapping to the right of the I-B subregion. HUL and HEL induce a cross-reactive suppressor cell, directed against a particular determinant found on both lysozymes. Once generated, these antigen-specific suppressor cells can affect the in vitro primary response to either lysozyme conjugated to sheep red blood cells. Despite this overlap, the strain distribution pattern of responsiveness is different for the two lysozymes. In the discussion, this was attributed to the MHC-related failure to process and/or present HEL to the HEL/HUL cross-reactive suppressor T cell in H-2q, d and u strains.