Analysis of Ig VH region genes encoding IgE antibodies in splenic B lymphocytes of a patient with asthma.
An atopic patient with hypersensitivity against house dust mite died as a result of an asthmatic attack. A portion of the spleen was obtained and was used to analyze the spectrum of Ig heavy chain V regions involved in encoding IgE Abs. A nested PCR technique generated 14 cloned VH sequences that had distinct CDR3 regions; 5 of 14 were derived from the minor VH5 family, and the remainder derived from the larger families, VH3 (6 of 14) and VH4 (3 of 14). One of the VH3-derived sequences was present as a repeated sequence in three clones. A control PCR with the same VH primers in combination with JH primers yielded only 1 of 13 sequences from VH5, indicating preferential VH5 usage only for IgE. Analysis of VH5-C epsilon sequences revealed usage of a single gene, DP73, with extensive mutations and several "hot spots" containing common replacement amino acids. However, there was no concentration of replacement mutations in the CDRs, which conventionally would indicate a role for Ag selection. The VH3 and VH4 genes in combination with C epsilon also harbored extensive somatic mutations. From these findings in splenic B lymphocytes, and those of a previous study of blood lymphocytes, it seems that preferential usage of VH5 genes and extensive somatic hypermutation are characteristic of B cells synthesizing IgE in patients with allergic disease.
Snow
R E
RE
Molecular Immunology Group, Tenovus Laboratory, Southampton University Hospitals, United Kingdom.
Chapman
C J
CJ
Frew
A J
AJ
Holgate
S T
ST
Stevenson
F K
FK
D000328:Adult; D000595:Amino Acid Sequence; D001249:Asthma / Q000235:genetics / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D001483:Base Sequence; D003001:Cloning, Molecular; D006801:Humans; D007073:Immunoglobulin E / Q000235:genetics*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D012689:Sequence Homology, Nucleic Acid; D013154:Spleen / Q000276:immunology
D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D007073:Immunoglobulin E