The effects of genes in the murine H2 region on basal immunoglobulin levels were investigated and ratios of IgG1/IgG2a were calculated, as low ratios indicate a Th1 cytokine mileu. H2(b) mice with B10 or BALE genetic backgrounds had higher levels of IgG2a than H2(k) and H2(d) congenic strains, and hence had low IgG1/IgG2a ratios. B10 (H2(h)) mice generally had high levels of IgG2b, IgG3, IgA and IgM, but this outcome was more variable. The high IgG2a phenotype was denoted Igis1 (Immunoglobulin isotype-1) and mapped telomeric of IE beta using B10.A(4R) mice thigh IgG2a) and B10.A(3R) and B10.A(5R) mice (low IgG2a). Further mapping in B10.A(2R), B10.A(1R) and B10.A(18R) mice placed Igis1 in the 27kb region between G7c and G7e.
Matthews, V. B., Christiansen, F., & Price, P. (2000). A novel locus affecting serum levels of IgG2a maps to the murine H2 region. European Journal of Immunogenetics, 27(3), 135-139. https://doi.org/10.1046/j.1365-2370.2000.00216.x