MOLECULAR MIMICRY - THE GEOGRAPHICAL-DISTRIBUTION OF IMMUNE-RESPONSESTO KLEBSIELLA IN ANKYLOSING-SPONDYLITIS AND ITS RELEVANCE TO THERAPY

The discovery that HLA-B27 is linked to ankylosing spondylitis (AS) an d HLA-DR1/DR4 to rheumatoid arthritis (RA) has provided new approaches to the study of the possible causation of these diseases. Several the ories have been proposed to explain these associations but only one, n amely ''molecular mimicry'', has provided a specific aetiological agen t for each of these diseases. Molecular mimicry between HLA-B27 and tw o molecules in Klebsiella microbes: nitrogenase and pullulanase D has been reported whilst in Proteus microbes, the haemolysin molecule show s sterochemical similarity to HLA-DR1/DR4. Elevated immune responses t o Klebsiella microbes have been demonstrated in AS patients from 10 di fferent countries and this wide geographical distribution suggests tha t the same aetiological agent is probably acting in producing this con dition. Furthermore RA patients show similar immune responses to Prote us microbes. Whether AS or RA are caused by these bacteria can only be resolved by tissue typing all rheumatological patients early, in the course of their disease and then assessing their response to antibioti c chemotherapy in longitudinal studies involving double-blind crossove r trials. It is possible that in the future, the course of AS or even RA could be modified by adequate antibiotic chemotherapy or even diets which affect the substrates on which these bacteria grow.