[Immunohistochemical Detection of Mast and Dendritic Cells in Periprosthetic Tissues of Aseptically Loosened Total Prostheses].

PURPOSE OF THE STUDY This study deals with the possibilities and application of immunohistochemical methods to detect mast and dendritic cells in periprosthetic tissues in patients with aseptically loosened total joint replacements of the knee and hip. The purpose of the study was to quantify and characterize the distribution of mast and dendritic cells in the examined samples and to study the statistically significant relations between the aforementioned cell populations and selected parameters characterizing the patients, implants or tissue response. Based on the proved findings, a possible relation between mast and dendritic cells and histomorphological patterns of aseptic loosening and the benefit of the applied immunohistochemical methods was evaluated. MATERIAL AND METHODS Periprosthetic tissues from a total of 31 patients (17 patients after a revision surgery of hip prosthesis, 14 patients after a revision surgery of knee prosthesis) were examined. The collected samples were processed according to the standard protocol for the purposes of histological and immunochemical examination. Antibodies against tryptase and CD117 were used for immunohistochemical detection of mast cells. Dendritic cells were detected by means of S100 and CD1a antibodies. Quantification of both the cell populations was carried out by optical microscopy in 20 high power fields at 400-times magnification. From among the applied methods we picked the more sensitive one for statistical evaluation. It was tryptase in the case of mast cells and S100 in the case of dendritic cells. RESULTS Mast and dendritic cells were mostly distributed dispersively in periprosthetic tissues; however, they also occurred in groups perivasally or near necrotic parts. The examined samples showed the presence of 60 mast cells and 50 dendritic cells on average. The increased density of mast and dendritic cells was associated with polypously formed pseudosynovium and cement fixation of prostheses; this relation was statistically significant. It was impossible to prove the correlation between the quantity of the observed cell populations and the nature and the number of the observed particles because wear particles were present dispersely in all the samples. Another statistically significant relation to the type of material or implant fixation or other examined histomorphological patterns was not proved. A strong density of mast cells with a minimum presence of dendritic cells was observed in the control patient group. DISCUSSION The differences in density of S100 positive dendritic cells between the control and examined group of patients can be caused by the activation of dendritic cells by exogenous or endogenous pathways of immune processes going on after the implantation of endoprosthesis. The statistically significant interrelation of mast cells, polypously formed pseudosynovium and cement wear particles can be explained at least in part as a tissue reaction induced by cement particles. CONCLUSIONS We proved the presence of two immunologically significant cell populations in periprosthetic tissues. The said findings indicate a conclusion of significant functional participation of mast and dendritic cells in pathogenesis of aseptic loosening and periprosthetic osteolysis. Nevertheless, this will have to be proved in another way and with the use of another method. Key words:dendritic cells, mast cells, aseptic loosening, total joint replacement, immune reaction, adverse reaction.