[Lead gout].

HLA-B27 confers a very strong genetic predisposition to development of a reactive arthritis after infection by bacteria such as Salmonella typhimurium. This study examines the role of HLA-B27 in the initiation of the earliest host activities after exposure to Salmonella, namely activation of the immediate early genes in the epithelial cells. Our major finding is that in Hela cells, the expression of c-fos was induced by Salmonella invasion only when the cells expressed the transfected HLA-B27 gene, but not the HLA-A1 gene or a truncated HLA-B27 gene lacking the exons encoding the cytoplasmic domain. C-fos is potentially capable of complexing with members of the c-jun family to become the AP-1 transcription complex. Parallel to c-fos expression, we found that only with the HLA-B27 transfectant was there expression of AP-1. AP-1 potentially controls the expression of a large number of genes. On screening a panel of proinflammatory molecules, we found that Salmonella invasion induced expression of monocyte chemoattractant protein-1 in the HLA-B27 cells. Since each of these separate positive findings belong to the same cascade of events after cell activation, together they reinforce the hypothesis that HLA-B27 plays a modulatory role in the early signal transduction events induced by Salmonella invasion. This hypothesis adds another item to the list of allele-specific activities carried out by HLA class I molecules. If similar activation also occurs in the joints, it may play a major role in arthritis.

Arthritis↗

PubMed1998

Orthopaedic manifestations of systemic disease.

Nuclear medicine studies can be initiated to detect or evaluate systemic diseases such as inflammatory arthritis or Paget's disease. This is usually because of the strengths of nuclear medicine studies such as high sensitivity, an ability to easily image the whole body, and typical diagnostic patterns of abnormalities. In other instances, a systemic disease may be incidentally suggested by a scintigram such as osteoporosis or hyperparathyroidism; or a focal abnormality such as a vascular necrosis may be detected that should indicate a systemic condition should be sought. Although most nuclear medicine studies have high sensitivity for disease, specificity is often less and, for a particular scan abnormality, several conditions may have to be considered. Familiarity with the varying patterns of abnormality associated with different disease is therefore vital to correct assessment.

Arthritis↗