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The HLA System

This issue of the British Medical Bulletin, edited by Professor Bodmer, provides a broad view of current knowledge in this field. The emphasis is on the possible clinical applications, but many of the sections will be hard going for most physicians. For the expert the report of the 7th International Histocompatibility Workshop and Conference will provide more comprehensive reading covering the same ground in more detail. The sections on HLA and various diseases are informative, and each section provides a summary of the known linkages in particular conditions. Those thinking of searching for disease associations would do well to take note of the comments in the introductory review by Dr Heather Dick pointing out the problems in designing studies on HLA linkage to disease. The lack of clinical value in requesting tissue typing in sporadic 'interesting' cases is surely clear to anyone reading this section. The paper on HLA ankylosing spondylitis and rheumatoid arthritis is important to all rheumatologists. The association ofHLA B27 with ankylosing spondylitis is by now common parlance, but the weaker association with HLA A2 is of interest, suggesting there are 2 possible susceptibility genes, one near the HLA B and another close to the HLA A. The strong linkage disequilibrium with HLA B27 also influences the incidence, form, and severity of the disease, but the precise effect in the closely associated rheumaric disorders is still open to speculation, in particular the interplay between the environmental factors and the genetic markers. The association of DW4 and DRW4 and HLA B15 with rheumatoid arthritis is now established but weak. Nevertheless it may be important in relation to disease severity. This issue is sound and will keep readers informed in this field, but it should be apparent that we are in the middle-or some would say at the beginning-of an exciting and evolving subject in which considerable discoveries have yet to be made.