B lymphocyte involvement in ankylosing spondylitis: the heavy chain variable segment gene repertoire of B lymphocytes from germinal center-like foci in the synovial membrane indicates antigen selection

The synovial membrane (SM) of affected joints in ankylosing spondylitis (AS)
is infiltrated by germinal center-like aggregates (foci) of lymphocytes similar
to rheumatoid arthritis (RA). We characterized the rearranged heavy chain
variable segment (VH) genes in the SM for gene usage and the mutational pattern
to elucidate the B lymphocyte involvement in AS.
Cryosections from an AS-derived SM were stained for B and T lymphocytes. B
cells were isolated from different areas of a focus. The rearranged VH genes
were amplified by semi-nested polymerase chain reaction (PCR) using
oligonucleotides specific for the six different VH families and heavy chain
joining segments (JHs). PCR products were cloned and sequenced.
Fifty-nine of 70 different heavy chain gene rearrangements were potentially
functional. Most of the rearranged genes were mutated (range, 1–15%). Thirty of
70 products had a mutational pattern typical for antigen selection. Most of the
rearranged VH genes belonged to the VH3 family (54%), consistent with data from
healthy donors and patients with RA, while VH4 genes, in contrast to RA, were
identified less frequently (10%) and VH5 genes were over-represented (11%). In
contrast to RA, neither VH6 genes nor the autoimmunity-prone VH4-34 were seen,
whereas another autoimmunity-prone gene, V3-23, was predominantly used (11%).
One VH1-derived and one VH3-derived B cell clone were expanded. CDR3 were
shorter and more variable in length than in RA.
Comparable with RA and reactive arthritis, there is a biased repertoire of
selected VH genes, whereas the panel of represented genes is different and less
clonal expansion was observed.