Analysis of immunoglobulin gamma heavy chain expression in synovial tissue of a patient with rheumatoid arthritis.
OBJECTIVE
To gain insight into mechanisms underlying local immune responses in rheumatoid arthritis (RA), we analyzed the utilization of variable-region heavy chain (VH), diversity (DH), and joining (JH) gene segments expressed in synovial tissue of a patient with RA.


METHODS
An unrestricted complementary DNA (cDNA) library was generated from unselected cells extracted from synovial tissue obtained at the time of joint replacement. Southern blot analysis for VH, JH, and C gamma subclass utilization was performed on the first 50 C gamma- and JH-positive recombinants for which phage DNA was isolated. Eighteen of the clones were selected at random for sequence analysis. The VH gene segments were compared with an extensive database of germline and cDNA sequences.


RESULTS
All transcripts utilized gene segments from the VH1 (28%), VH3 (56%), and VH4 (15%) families. There was a predominance of JH4, JH5, and JH6 gene segment utilization. Fourteen of 18 randomly sequenced clones contained sufficient VH-region information for analysis. Eight (57%) were most closely related to VH gene segments that are preferentially expressed in human fetal liver or that encode antibodies with self-reactivity. The variable domains were heavily mutated, and replacement-to-silent substitution ratios (R:S ratios) in the antigen-binding domains (complementarity-determining regions [CDRs]) were disproportionately high. CDR3 lengths were quite variable, due to extensive N-region addition and 5'-exonuclease activity in the VH-DH-JH joins.


CONCLUSIONS
Plasma cells in this synovial tissue sample appear to express VH gene segments that are preferentially utilized during fetal development or in autoantibodies. The JH repertoire is similar to that seen in adult peripheral blood lymphocytes, but much different from that found during fetal development. The large number of somatic mutations and the high R:S ratios in the CDRs suggest an antigen-driven response.
Bridges
S L
SL
Department of Medicine, University of Alabama, Birmingham 35294.
Lee
S K
SK
Koopman
W J
WJ
Schroeder
H W
HW
D000595:Amino Acid Sequence; D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000276:immunology*; D001483:Base Sequence; D015723:Gene Library; D006801:Humans; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D007142:Immunoglobulin gamma-Chains / Q000235:genetics*; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D013583:Synovial Membrane / Q000166:cytology / Q000276:immunology*; D014158:Transcription, Genetic
D007135:Immunoglobulin Variable Region; D007142:Immunoglobulin gamma-Chains