title: Positive selection of the peripheral B cell repertoire in gut-associated lymphoid tissues.
abstract: Gut-associated lymphoid tissues (GALTs) interact with intestinal microflora to drive GALT development and diversify the primary antibody repertoire; however, the molecular mechanisms that link these events remain elusive. Alicia rabbits provide an excellent model to investigate the relationship between GALT, intestinal microflora, and modulation of the antibody repertoire. Most B cells in neonatal Alicia rabbits express V(H)n allotype immunoglobulin (Ig)M. Within weeks, the number of V(H)n B cells decreases, whereas V(H)a allotype B cells increase in number and become predominant. We hypothesized that the repertoire shift from V(H)n to V(H)a B cells results from interactions between GALT and intestinal microflora. To test this hypothesis, we surgically removed organized GALT from newborn Alicia pups and ligated the appendix to sequester it from intestinal microflora. Flow cytometry and nucleotide sequence analyses revealed that the V(H)n to V(H)a repertoire shift did not occur, demonstrating the requirement for interactions between GALT and intestinal microflora in the selective expansion of V(H)a B cells. By comparing amino acid sequences of V(H)n and V(H)a Ig, we identified a putative V(H) ligand binding site for a bacterial or endogenous B cell superantigen. We propose that interaction of such a superantigen with V(H)a B cells results in their selective expansion.
authors.affiliation: Department of Microbiology and Immunology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA.
authors.forename: Ki-Jong
authors.initials: KJ
authors.lastname: Rhee
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Jasper
authors.forename: Periannan
authors.initials: P
authors.lastname: Sethupathi
authors.forename: Malathy
authors.initials: M
authors.lastname: Shanmugam
authors.forename: Dennis
authors.initials: D
authors.lastname: Lanning
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Knight
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D005803:Genes, Immunoglobulin / Q000235:genetics; D007126:Immunoglobulin Allotypes / Q000276:immunology / Q000378:metabolism*; D017578:Immunoglobulin Class Switching / Q000235:genetics* / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology / Q000378:metabolism*; D007135:Immunoglobulin Variable Region / Q000096:biosynthesis / Q000235:genetics*; D008221:Lymphoid Tissue / Q000276:immunology* / Q000382:microbiology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011817:Rabbits; D017422:Sequence Analysis, DNA; D018089:Superantigens / Q000235:genetics
chemical_list: D018076:DNA, Complementary; D007126:Immunoglobulin Allotypes; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region; D018089:Superantigens; D002118:Calcium