title: Development of B cells producing natural autoantibodies to thymocytes and senescent erythrocytes.
abstract: Natural antibodies produced by CD5+ B-1 B cells include those with specificity for senescent erythrocytes (anti-BrMRBC, anti-PtC) and for thymocytes (anti-thymocyte autoantibody, ATA). Here we describe work from our laboratories studying two prototypic examples, V(H)11Vkappa9-encoded anti-BrMRBC and V(H)3609Vkappa21c-encoded ATA. Using V(H)11-mu transgenic mice, we discovered that certain natural autoantibodies utilize V(H) genes that are selected against in bone marrow B cell development, but not fetal liver, effectively restricting their generation to fetal/neonatal life. Studies with ATA-mu transgenic mice demonstrated a critical requirement for self antigen in the accumulation of B cells with this specificity and for the production of high levels of serum ATA. Finally, analysis of B cell development in ATA-mu kappa transgenic mice revealed two distinct responses by B cells to expression of this B cell receptor (BCR): most developing B cells in spleen of adult mice were blocked at an immature stage and only escaped apoptosis by editing their BCR to eliminate the ATA specificity; nevertheless, high levels of serum ATA were observed, indicating that some B cells differentiated to antibody-forming cells without altering their specificity. Thus, our studies reveal mechanisms for restricting the generation of B cells producing natural autoantibodies, demonstrate a key positive selection step in their development, and show that most developing B cells in adult mice bearing such specificities fail to reach a mature stage.
authors.affiliation: Division of Basic Sciences, Fox Chase Cancer Center, 333 Cottman Ave., Philadelphia, PA 19111, USA. rr_hardy@fccc.edu
authors.forename: Richard R
authors.initials: RR
authors.lastname: Hardy
authors.forename: Kyoko
authors.initials: K
authors.lastname: Hayakawa
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D000961:Antilymphocyte Serum / Q000096:biosynthesis; D001323:Autoantibodies / Q000096:biosynthesis; D016175:B-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology*; D002454:Cell Differentiation; D004905:Erythrocyte Aging; D004912:Erythrocytes / Q000276:immunology; D007113:Immunity, Innate; D051379:Mice; D008822:Mice, Transgenic; D018448:Models, Immunological; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D000961:Antilymphocyte Serum; D001323:Autoantibodies; D011947:Receptors, Antigen, B-Cell