LOCAL IMMUNE INFLAMMATORY RESPONSE TO INFECTED TOTAL HIP AND KNEE REPLACEMENTS

We studied the tissue response for periprosthetic pseudosynovial tissu e in seven patients with a purulent endoprosthetic infection and six p atients with common prosthesis loosening, using specific monoclonal an tibodies in avidin-biotin-peroxidase complex staining. In infected cas es, proline 4-hydroxylase positive fibroblasts dominated the stroma of the vascularized periprosthetic connective tissue, whereas diffuse lo cal infiltrations of mononuclear cells characterized the cellular hist ological overview. Local cellular response consisted of CD11b and MHC locus II antigen-positive immunoreactive monocytes/macrophages and of T lymphocytes, mostly of the CD4 subset. Only a few CD25-positive cell s could be detected. The local cellular response in six patients with prosthesis loosening of nonbacterial origin was mild, showing a sparse perivascular infiltration of CD11b- and Ia-positive monocytes/macroph ages and CD4/CD8-positive T lymphocytes in a proportion of 2:1. Only o ccasional CD15- or lactoferrin-positive neutrophils and CD25-positive lymphocytes could be detected. Our results from chronically infected j oint replacements suggest that neutrophils, being virtually absent in the tissue compartment, do not contribute to pathological events in th e ''pseudojoint'' cavity, wheras local tissue response consists of a m ononuclear inflammatory cell reaction of a macrophage-dependent foreig n-body type.