The little brown bat, M. lucifugus, displays a highly diverse VH, DH and JH repertoire but little evidence of somatic hypermutation

Myotis lucifugus populations in Northeastern US are being decimated by a fungal disease. Since almost nothing is known about the immune system of bats, we are characterizing the immunoglobulin genes of bats. We show that M. lucifugus has a diverse VH gene repertoire comprised of five of the seven human VH gene families and an estimated 236 VH3 genes. 95% of these germline VH3 genes differ in FR3. A comparison of 67 expressed VH3 genes with 75 germline VH3 genes revealed a mutation frequency similar to fetal piglets never exposed to environmental antigens. Analysis of CDR3 regions identified at least 13 putative JH segments and a large DH repertoire. The low mutation frequency, highly diverse VH, DH, and JH germline repertoire suggests that this species may rely more on combinatorial and junctional diversity than on somatic hypermutation raising questions about the ability of M. lucifugus to respond rapidly to emerging pathogens.