MONOCLONAL IMMUNOGLOBULIN-A DERIVED FROM PERITONEAL B-CELLS IS ENCODED BY BOTH GERM-LINE AND SOMATICALLY MUTATED V-H GENES AND IS REACTIVE WITH COMMENSAL BACTERIA

We transferred peritoneal cells from BALB/c mice into C.B17 scid/scid mice, Six to eight months after injection, only cells with the B1 phen otype were retained in the spleens and peritoneal cavities of these mi ce. The lamina propria of the intestine contained many peritoneal, don or-derived, immunoglobulin A (IgA)-producing cells, The mesenteric lym ph 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 bact erial populations, Cloning and sequencing of the V-H genes of these hy bridomas showed that two hybridomas utilized germ line-encoded V-H gen es while the V-H genes of the other six hybridomas showed somatic muta tions, some of which are indicative of an antigen-driven selection pro cess.