CD68+ macrophages as crucial components of the foreign body reaction demonstrate an unconventional pattern of functional markers quantified by analysis with double fluorescence staining

Implants like meshes for the reinforcement of tissues implement the formation of a persistent inflammation with an ambient fibrotic reaction. In the inflammatory infiltrate several distinct cell types have been identified, but CD68+ macrophages are supposed to be most important. To investigate the collaboration among the various cell types within the infiltrate we performed at explanted meshes from humans double fluorescence staining with CD68 as a constant marker and a variety of other antibodies as the second marker. The list of second markers includes lymphocytes (CD3, CD4, CD8, CD16, CD56, FoxP3, and CD11b) stem cells (CD34), leucocytes (CD45, CD15), macrophages (CD86, CD105, CD163, and CD206); deposition of EC matrix (collagen-I, collagen-III, MMP2, and MMP8); Ki67 as a marker for proliferation; and the tyrosine-protein kinase receptor AXL. The present study demonstrates within the inflammatory infiltrate the abundant capability of CD68+ cells to co-express a huge variety of other markers, including those of lymphocytes, varying between 5 and 83% of investigated cells. The observation of co-staining was not restricted to a specific polymer but was seen with polypropylene fibers as well as with fibers made of polyvinylidene fluoride, although with differences in co-expression rates. The persisting variability of these cells without the functional reduction toward differentiated mature cell types may favor the lack of healing at the interface of meshes.