MARJATTA LEIRISALO, HEIKKI REPO, ANJA TIILIKAINEN, T I M 0 U. KOSUNEN, and OSSI LAITINEN Chemotaxis, chemokinesis, and spontaneous locomotion of polymorphonuclear leukocytes (PMNs) of yersinia arthritis (YA) patients and healthy subjects with or without HLA-B27 were studied by agarose assay and membrane filter technique. HLA-B27 positive healthy control subjects and yersinia patients showed significantly higher response to chemotactic stimulus than HLA-B27 negative controls. Consequently, the high response was associated with HLA-B27 irrespective of YA. The high responder PMNs may contribute to the more severe inflammatory symptoms in YA patients with HLA-B27.Reactive arthritis is a form of nonpurulent arthritis following an infection elsewhere in the body. In addition to rheumatic fever, a sequel of streptococcal pharyngitis, reactive arthritis can follow some enteric or urogenital infections such as Yersiniu enterocoliticu (I), salmonella (2), shigella (3), chlamydia (4), or cam-~