Prosthetic joint infection (PJI) has continued as a leading cause of hip arthroplasty failure often associated with Staphylococcus aureus as the pathogen. Staphylococcus aureus biofilm infections are characterized by the accumulation of granulocyte myeloid-derived suppressor cells (G-MDSCs) that are pathologically activated polymorphonuclear cells (PMNs) and defined by their ability to suppress the proinflammatory activity of other immune cells (T cells, macrophages, and PMNs). The purpose of this study was to identify what factors may contribute to the pathologic suppression in PJI. Materials and Methods Synovial fluid and matched pre- and post-surgical blood samples were collected from patients with and without PJI. Flow cytometry, multianalyte microbead array, and ELISA were performed. Statistics to detect significant differences between aseptic and septic samples were determined. Results Two MDSCs subtypes were identified; monocytic MDSCs and G-MDSCs. Although the percentages of CD45+ leukocytes were not affected by surgery the granulocytic fraction was elevated. Collectively, the observed increase in G-MDSCs and PMNs reflected a transition toward an increased granulocytic population. This was reflected by elevated IL-10 production and decreased CD4+ T cells, both suggestive of G-MDSC activity. Conclusion The findings of PMN expansion and CD4+ T cell contraction after arthroplasty agree with prior studies reporting increased neutrophil to lymphocyte ratios in hip and knee patients in the post-operative interval. IL-10 production may enhance patient susceptibility to infectious complications. Additionally, elevated IL-10 levels have been associated with impaired long-term care functional performance in patients with bone injuries which were predictive of later sepsis development.
Kielian et al. (Thu,) studied this question.