Monoclonal immunoglobulin a derived from peritoneal b cells is encoded by both germ line and somatically mutated VH genes and is reactive with commensal bacteria

Abstract

We transferred peritoneal cells from BALB/c mice into C.B17 scid/scid mice. Six to eight months after injection, only cells with the Bl phenotype were retained in the spleens and peritoneal cavities of these mice. The lamina propria of the intestine contained many peritoneal, donor-derived, immunoglobulin A (IgA)-producing cells. The mesenteric lymph nodes of these mice were found to be a major site of proliferation and generation of IgA plasmablasts. We established eight IgA-producing hybridomas from the mesenteric lymph nodes of such mice, and all the hybridomas reacted with different but partially overlapping fecal bacterial populations. Cloning and sequencing of the VH genes of these hybridomas showed that two hybridomas utilized germ line-encoded VH genes while the VH genes of the other six hybridomas showed somatic mutations, some of which are indicative of an antigen-driven selection process.