Restricted kappa chain expression in early ontogeny: biased utilization of V kappa exons and preferential V kappa-J kappa recombinations.
To determine the extent of kappa chain diversity in the preimmune repertoire early in development, kappa cDNA libraries were analyzed from 15-d old fetal omentum, 18-d-old fetal liver, and 3-wk old bone marrow. An anchored polymerase chain reaction approach was used to avoid bias for particular V kappa families. From the sequence analysis of 27 bone marrow clones, 10 different families and 20 unique V kappa genes were identified. In contrast, the V kappa expression in the fetus is highly restricted and clearly differs from the broader distribution see in 3-wk-old bone marrow. Although several V kappa families were represented in the fetal library including V kappa 9, V kappa 10, V kappa 4,5, V kappa 8, and V kappa 1, one or two members of individual families were observed repeatedly. The fetal liver and omentum libraries were found to be largely overlapping. Given the V kappa families/exons identified in the fetal sequences, the mechanism of kappa rearrangements in the early repertoire appears to occur predominantly by inversion. Importantly, the fetal repertoire was further restricted by dominant V kappa-J kappa combinations such as V kappa 4,5-J kappa 5, V kappa 9-J kappa 4, and V kappa 10-J kappa 1. Since in some cases independent rearrangements could be established, the results indicate a bias for particular V kappa-J kappa joins. The results also suggest that clonal expansion/selection in the fetal repertoire takes place after light chain rearrangement as opposed to at the pre-B cell level in the bone marrow. The restriction observed in kappa light chain expression together with known restrictions in gene usage and junctional diversity at the heavy chain level indicate a remarkably conserved fetal repertoire.
Medina
C A
CA
Department of Microbiology, University of Texas Health Science Center, San Antonio 78284-7758.
Teale
J M
JM
D000595:Amino Acid Sequence; D000818:Animals; D000916:Antibody Diversity / Q000235:genetics; D001483:Base Sequence; D001853:Bone Marrow / Q000276:immunology; D004247:DNA; D005091:Exons; D015870:Gene Expression; D015328:Gene Rearrangement, B-Lymphocyte, Light Chain; D007133:Immunoglobulin Joining Region / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D007145:Immunoglobulin kappa-Chains / Q000096:biosynthesis* / Q000235:genetics; D008099:Liver / Q000196:embryology / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009852:Omentum / Q000196:embryology
D007133:Immunoglobulin Joining Region; D007135:Immunoglobulin Variable Region; D007145:Immunoglobulin kappa-Chains; D004247:DNA