The role of gene deletion in the immunoglobulin heavy chain switch.

We have examined the arrangement of the genes for the mouse heavy chain subclasses gamma 2b, gamma 2a and gamma 1 by the Southern hybridisation procedure. Evidence has been found for rearrangement involving the gamma 2b and gamma 2a CH genes in the DNA of cells making IgG2b and IgG2a respectively. The DNA of an IgG2b-secreting line lacks detectable C gamma 1 gene, whilst the DNA of an IgG2a-secreting line lacks detectable C gamma 1 and C gamma 2b genes. The DNA of a cell line secreting IgA lacks detectable C gamma genes. These observations implicate deletion in the mechanism of the H-chain switch and allow a preliminary ordering of some of the CH genes in the mouse genome.