title: CD5+ peritoneal B cells express high levels of membrane, but not secretory, C mu mRNA.
abstract: We used in situ hybridization to study Ig mRNA levels in murine peritoneal and splenic B cells. Ig mRNA production fell into three distinct groups: low, intermediate, and high. Splenic B cells primarily exhibited low levels characteristic of resting B cells or high Ig mRNA levels characteristic of plasma cells. In contrast, a significant fraction of peritoneal B cells exhibited intermediate Ig mRNA levels. Intermediate Ig mRNA was T cell dependent in that congenic nu/nu mice had far fewer peritoneal cells expressing the intermediate Ig message than their wild type counterparts. CD5+ CD11b+ IgMbright+ peritoneal B cells were found to be mainly responsible for the production of intermediate Ig mRNA levels. The peritoneal CD5- CD11b+ IgMbright+ "sister" B cell subpopulation contained a lower percentage of intermediate Ig mRNA-producing B cells. CD5-CD11b-IgMdull+ "conventional" B cells produced negligible levels of Ig mRNA, comparable to those of unfractionated splenic B cells. Northern analysis showed that the majority of Ig mRNA expressed in the peritoneum is of the membrane rather than the secreted form. Consistent with that result, in short-term culture, peritoneal cells showed markedly less Ig secretion than did spleen cells. These studies describe novel Ig mRNA expression by peritoneal B cells and emphasize that within the peritoneal cavity, B cells do not tend to become antibody-secreting cells.
authors.affiliation: Cellular Immunology Section, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892.
authors.forename: T M
authors.initials: TM
authors.lastname: McIntyre
authors.forename: K L
authors.initials: KL
authors.lastname: Holmes
authors.forename: A D
authors.initials: AD
authors.lastname: Steinberg
authors.forename: D L
authors.initials: DL
authors.lastname: Kastner
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000032:analysis*; D000943:Antigens, Differentiation / Q000032:analysis*; D001402:B-Lymphocytes / Q000276:immunology*; D015152:Blotting, Northern; D018956:CD5 Antigens; D005434:Flow Cytometry; D007075:Immunoglobulin M / Q000235:genetics* / Q000378:metabolism; D016177:Macrophage-1 Antigen / Q000032:analysis; D051379:Mice; D008815:Mice, Inbred Strains; D010529:Peritoneal Cavity / Q000166:cytology*; D012333:RNA, Messenger / Q000032:analysis*; D013045:Species Specificity
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D018956:CD5 Antigens; D007075:Immunoglobulin M; D016177:Macrophage-1 Antigen; D012333:RNA, Messenger