Variable region gene analysis of pathologic human autoantibodies to the related i and I red blood cell antigens.
To investigate the molecular basis of the autoimmune response to the related i and I carbohydrate antigens, we studied cold agglutinins (CA) from B-cell clones and from the peripheral circulation of patients with lymphoproliferative syndromes. Sequence analyses of expressed variable region genes indicate that both anti-i and anti-I specificities from B-cell clones from two patients are encoded by the VH4.21 or a very closely related VH4 heavy chain gene, whereas the expressed light chain genes differed. The anti-i-secreting B-cells express unmutated germline-encoded VH4.21 and VKI gene sequences. The VH region gene encoding anti-I has the closest homology (97%) to the VH4.21 germline gene and differs at the protein level by only three amino acids. In contrast, while the VL region gene encoding anti-I is most homologous (96%) to the VKIII, kv328 germline gene, there are seven amino acid differences due to nonrandom replacement mutations, which suggests a role for antigen-mediated selection in the anti-I response of this individual. These studies were extended by a structural survey of 20 additional serum CA using antipeptide antibodies specific for determinants in VH and VL regions. All anti-I and anti-i CA were shown to express VH4 heavy chains, and 14 of 17 CA expressed a previously described VH4 second hypervariable region determinant, termed VH4-HV2a. We also found that 13 of 14 anti-I CA used VKIII light chains, while the anti-i CA used light chains from at least three VL families. Taken together, the data show that anti-i and anti-I CA probably both derive from the VH4.21 gene (or a closely related gene). Furthermore, the restricted VH and different VL gene use in anti-i and anti-I CA may reflect the close structural relationship of the i and I antigens.
Silberstein
L E
LE
Department of Pathology and Laboratory Medicine, University of Pennsylvania, School of Medicine, Philadelphia.
Jefferies
L C
LC
Goldman
J
J
Friedman
D
D
Moore
J S
JS
Nowell
P C
PC
Roelcke
D
D
Pruzanski
W
W
Roudier
J
J
Silverman
G J
GJ
D001323:Autoantibodies / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D001483:Base Sequence; D015139:Blotting, Southern; D002461:Cell Line, Transformed; D002999:Clone Cells; D003001:Cloning, Molecular; D003080:Cold Temperature; D004247:DNA / Q000235:genetics; D004912:Erythrocytes / Q000276:immunology; D005434:Flow Cytometry; D004854:Herpesvirus 4, Human; D006801:Humans; D007048:I Blood-Group System / Q000276:immunology*; D015151:Immunoblotting; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007130:Immunoglobulin Idiotypes / Q000276:immunology; D007147:Immunoglobulin Light Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D008232:Lymphoproliferative Disorders / Q000276:immunology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction
D001323:Autoantibodies; D007048:I Blood-Group System; D007143:Immunoglobulin Heavy Chains; D007130:Immunoglobulin Idiotypes; D007147:Immunoglobulin Light Chains; D007135:Immunoglobulin Variable Region; D004247:DNA