Relationship of variable region genes expressed by a human B cell lymphoma secreting pathologic anti-Pr2 erythrocyte autoantibodies.
To study the biology of cold agglutinin disease we previously established EBV-transformed B cell clones isolated from a patient with splenic lymphoma of an early plasmacytic cell type and immune hemolysis due to an anti-Pr2 cold agglutinin. These clones had an aberrant chromosomal marker identical to the patient's B cell lymphoma and each secreted IgMk anti-Pr2 similar to the pathologic autoantibody in the serum of the patient. In this study, we have further investigated the Pr2-specific autoimmune response through nucleotide sequencing of VH and VL region genes. We have shown that the seven clones share the same VDJ/VJ gene segments and junctional elements confirming their clonal origin. The VH sequences were 88% homologous to a VHI germline gene while the VL sequences were 97% homologous to a VkIII germline gene. Only 4 somatic mutations (3 silent and 1 conservative) were found in greater than 5,000 bp sequenced, suggesting that a low mutation rate existed. Based on a tumor mass of 10(12) cells and a minimum of 40 divisions, we estimated the somatic mutation rate to be 4.45 x 10(-5) m/bp/d. This somatic mutation rate is similar to those estimated for acute lymphocytic leukemia (pre-B cell) and chronic lymphocytic leukemia (intermediate B cell), but significantly lower than the mutation frequency in follicular lymphomas (activated B cell). We propose that the difference in somatic mutation frequency of a B cell tumor may be related to the stage of B cell differentiation. In addition, the low mutation frequency observed in the Pr2-specific B cell tumor may also reflect, in part, selection by autoantigen to conserve sIg structure and specificity.
Silberstein
L E
LE
Department of Pathology and Laboratory Medicine, School of Medicine, University of Pennsylvania, Philadelphia 19104-4283.
Litwin
S
S
Carmack
C E
CE
D000373:Agglutinins / Q000235:genetics* / Q000276:immunology; D000595:Amino Acid Sequence; D000744:Anemia, Hemolytic, Autoimmune / Q000276:immunology*; D001323:Autoantibodies / Q000235:genetics* / Q000276:immunology; D001402:B-Lymphocytes; D001483:Base Sequence; D002461:Cell Line, Transformed; D003001:Cloning, Molecular; D003450:Cryoglobulins; D004912:Erythrocytes / Q000276:immunology; D005803:Genes, Immunoglobulin; D004854:Herpesvirus 4, Human; D006801:Humans; D007075:Immunoglobulin M / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D007145:Immunoglobulin kappa-Chains / Q000276:immunology; D008223:Lymphoma / Q000276:immunology*; D008969:Molecular Sequence Data; D009154:Mutation; D012689:Sequence Homology, Nucleic Acid; D014407:Tumor Cells, Cultured
D000373:Agglutinins; D001323:Autoantibodies; D003450:Cryoglobulins; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region; D007145:Immunoglobulin kappa-Chains; C029443:cold agglutinins