Mutual homology of mouse immunoglobulin .gamma.-chain gene sequences

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Abstract
The relative homology of mouse immunoglobulin H chain gene sequences was assessed using complementary[c]DNA synthesized against .gamma.-chain mRNA (.gamma.1, y2a, .gamma.2b, and .gamma.3) purified from mouse myelomas. cDNA complementary to the .gamma.-chain mRNA did not cross-hybridize with the .mu.- and .alpha.-chain mRNA, but they did cross-hybridize to significant extents (22-66%) with the .gamma.-chain mRNA of other subclasses. The heterologous hybrids formed, melt at 5-13.degree. C lower temperatures as compared to the homologous hybrids, indicating that significant portions of the heterologous hybrids are mismatched. The rates of the cross-hybridization reactions are 2-17 times slower than those of the homologous hybridization reactions. The .gamma.-chain gene sequences of 4 subclasses are somewhat homologous, but are different enough to be measured separately. Cross-hybridization analyses indicate that the .gamma.2a and .gamma.2b genes are the most closely related, while the .gamma.1 and .gamma.3 genes are the least related among the .gamma. subclass genes.