The sera of patients with Klebsiella infections contain a common anti-DNA idiotype (16/6) Id and anti-polynucleotide activity.

In view of recent reports linking Klebsiella pneumoniae with autoimmunity, we have examined the sera of 52 patients with urinary tract infection or septicaemia from this Gram-negative pathogen, for the presence of antibodies to DNA, polynucleotides, cardiolipin and a common anti-DNA idiotype 16/6. Up to 27% of these patients had anti-polynucleotide antibodies detectable, and in 37% the 16/6 idiotype was found. Absorption of the sera of two patients, with no DNA binding, against the Klebsiella polysaccharide K-30 induced a significant fall in both their anti-K30 antibody and 16/6 idiotype levels. Among 52 patients with other Gram negative infections a maximum of 17% and 19% respectively, had anti-DNA antibodies and the 16/6 idiotype present in their serum. In 37 normal controls, the rate of antibody and idiotype detection was 5% or less. The presence of autoantibodies in the serum of patients with Klebsiella infections may be the result of non-specific stimulation due to bacterial polyclonal activation. However, there might also be a specific stimulus triggered by idiotypic cross-reaction between autoantibodies and anti-Klebsiella antibodies.