VHDJH gene sequences and antigen reactivity of monoclonal antibodies produced by human B-1 cells: evidence for somatic selection.
To understand whether the distinct VHDJH gene utilization by natural polyreactive Abs reflects the developmentally restricted Ig VHDJH rearrangements putatively expressed by B-1 cells, we generated 11 (8 IgM, 1 IgG3, 2 IgA1), 7 (6 IgM, 1 IgG1), and 7 (2 IgM, 3 IgG1, 2 IgG3) mAb-producing lines using B-1a (surface CD5+, CD45RAlow), B-1b (surface CD5-, CD45RAlow, CD5 mRNA+), and B-2 (surface CD5-, CD45RAhigh, CD5 mRNA-) cells, respectively, sorted from adult human peripheral blood. Most B-1a and B-1b, but no B-2, cell-derived mAbs were polyreactive; i.e., they bound different self and foreign Ags with different affinities. B-1a and B-2 mAbs preferentially utilized VH4 (p = 0.003) and VH3 (p = 0.010) genes, respectively. All three mAb populations utilized DXP, DLR, DN DH genes, and JH6, but no mAb utilized DHQ52. There were fewer unencoded nucleotide (N) additions in the VHDJH junctions of B-1b (3.00 +/- 2.52, mean +/- SD) than of B-1a (12.45 +/- 3.93, p = 1.23 x 10(-5)) or B-2 (8.29 +/- 4.75, p = 0.020) mAbs. Partly due to the fewer N additions and a paucity of D-D fusions, the B-1b mAb CDR3s were significantly shorter than the B-1a mAb CDR3s (p = 0.013), which contained a nonrandom Tyr distribution (p = 0.003). Finally, all but two B-1 cell-derived mAbs were mutated, in a fashion similar to that of the Ag-selected B-2 mAbs. Thus, in the human adult, B-1 cells that make natural polyreactive Abs may not be representative of the predominantly B-1 developmental waves of colonization of the fetal and neonatal B cell repertoires, and are somatically selected.
Schettino
E W
EW
Department of Pathology, Cornell University Medical College, New York 10021, USA.
Chai
S K
SK
Kasaian
M T
MT
Schroeder
H W
HW
Casali
P
P
D000328:Adult; D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D000937:Antigen-Antibody Reactions; D016175:B-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism*; D001483:Base Sequence; D018956:CD5 Antigens / Q000235:genetics; D002460:Cell Line; D005803:Genes, Immunoglobulin / Q000276:immunology*; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D007133:Immunoglobulin Joining Region / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D017354:Point Mutation / Q000276:immunology; D012333:RNA, Messenger / Q000096:biosynthesis
D000911:Antibodies, Monoclonal; D018956:CD5 Antigens; D007143:Immunoglobulin Heavy Chains; D007133:Immunoglobulin Joining Region; D007135:Immunoglobulin Variable Region; D012333:RNA, Messenger