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 V_H gene repertoire comprised of five of the seven human V_H gene families and an estimated 236 V_H3 genes. 95% of these germline VH3 genes differ in FR3. A comparison of 67 expressed V_H3 genes with 75 germline V_H3 genes revealed a mutation frequency similar to fetal piglets never exposed to environmental antigens. Analysis of CDR3 regions identified at least 13 putative J_H segments and a large D_H repertoire. The low mutation frequency, highly diverse V_H, D_H, and J_H 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.