A factor(s) in Klebsiella culture filtrates specifically modifies an HLA-B27-associated cell-surface component

We have previously shown1,2 that a serum raised against certain isolates of Klebsiella pneumoniae lyses the lymphocytes of HLA-B27-positive patients with ankylosing spondylitis (AS) but not of B27-positive or B27-negative healthy controls. These observations suggested that some Klebsiella antigens cross-react with a gene product intimately associated with B27 or possibly with ‘modified’ B27 (refs 1, 3) in patients with AS. It seems likely therefore, that some Klebsiella antigens play a role in the pathogenesis of AS, perhaps by specifically modifying a B27-associated cell-surface marker. We have now examined the influence of culture filtrates from three Klebsiella isolates on lymphocytes from B27-positive and B27-negative healthy individuals. We report that 24-h culture filtrates of Klebsiella K43 (previously Klebsiella F19) contain a factor(s) capable of specifically modifying the sensitivity to anti-Klebsiella K43 serum of B27+AS− lymphocytes (that is, cells not lysed by anti-Klebsiella K43 serum): ‘modified’ B27+AS− lymphocytes are now serologically similar to the cells of B27-positive patients with AS (B27+AS+). The failure of anti-Klebsiella F10 and of anti-Escherichia coli sera to lyse lymphocytes, which have been incubated with the corresponding culture filtrates, excludes a nonspecific lysis by the anti-bacterial sera of target lymphocytes bearing bacterial antigens randomly distributed on their surface. Therefore, the data are compatible with a specific transformation by a Klebsiella K43-derived soluble factor of a B27-associated lymphoid cell component.