Paracrine and juxtacrine lymphocyte enhancement of adherent macrophage and foreign body giant cell activation

Lymphocytes have been shown to be involved in modulating monocyte and macrophage behavior in the foreign body reaction. Lymphocyte effects on biomaterial-adherent macrophage and foreign body giant cell (FBGC) behavior were further investigated by culturing monocytes alone or together with lymphocytes, either in direct co-cultures or indirectly in transwells, on a series of polyethylene terephthalate-based photograft co-polymerized material Surfaces displaying distinct hydrophobic, hydrophilic/neutral, hydrophilic/anionic, and hydrophilic/cationic chemistries. After periods of 3, 7, and 10 days, cytokine production was quantified by enzyme-linked immunosorbent assay and normalized to adherent macrophage/FBGC density to yield a measure of adherent macrophage/FBGC activation. Interactions with lymphocytes enhanced adherent macrophage and FBGC production of pro-inflammatory IL-1 beta, TNF-alpha, IL-6, IL-8, and MIP-1 beta on the hydrophobic and hydrophilic/cationic surfaces but had no effect on anti-inflammatory IL-10 production indicating lymphocytes promote a pro-inflammatory response to biomaterials. Lymphocytes also did not significantly influence MMP-9, TIMP-1, and TIMP-2 production. Interactions through indirect (paracrine) signaling showed a significant effect in enhancing adherent macrophage/FBGC activation at early time points whereas interactions via direct (juxtacrine) mechanisms dominated at later time points. Biomaterial surface chemistries differentially affected the observed responses as hydrophilic/neutral and hydrophilic/anionic surfaces, evoked the highest levels of activation relative to the other surfaces but did not facilitate lymphocyte enhancement of adherent macrophage/FBGC activation. (C) 2008 Wiley Periodicals, Inc. j Biomed Mater Res 89A: 490-498, 2009