Previous studies have shown that the periprosthetic metal content decisively determines the immunological response. Tissues with higher metal content (Co, Cr, and Ni) (222.2 ± 52.9 μg/g) showed a predominantly lymphoid cell response, whereas tissues with lower metal content (3.0 ± 0.9 μg/g) showed a macrophage-dominated cell response. Serum metal content did not correlate with this response, suggesting a local process (Lohmann et al. J Bone Joint Surg Am 2013). Another study further investigated this difference between the two responses by analyzing the cytokine profile of the periprosthetic tissue. It was shown that in the lymphocyte-domain cell response, there were high levels of IL-1ß, IL-5, IL-10, and GM-CSF compared to control tissues (Singh et al., Bone Joint J 2015). Furthermore, it has been shown that the resulting metal attrition also leads to a significant increase in the expression of CXCR4. CXCR4 is of critical importance in bone metastasis, inflammatory and autoimmune processes (Drynda et al, J Biomed Mater Res A 2015). This finding supports the hypothesis that the resulting metal particles directly mediate inflammatory processes.

A recent work also deals with the influence of PMMA bone cement particles on the immune system. This work describes that in PMMA spacers in the synovium and periprosthetic tissue lead to an increase in CD-11c positive dentritic cells, as well as CD-3 positive T cells, but also lead to a decrease in CD-20 positive B cells (Singh et al., Bone Joint J 2016).

This work shows a distinct immunological response to metal and plastic wear particles in periprosthetic tissue. The aim of the projects is to better understand these processes and to delay or prevent prosthesis blockage by interrupting the inflammatory signals.