T Cell Interactions in the Foreign Body Response to Biomaterials

Synthetic biomaterials are considered to be non-immunogenic. Therefore, the role that adaptive immunity may play in the host response to implanted synthetic biomaterials has not been extensively studied. Cardinal features of adaptive immunity include specificity and T cell responses which are greater and more effective with up-regulation of activation receptors upon re-challenge. We compared the primary and secondary in vivo host response to three synthetic biomaterials: Elasthane 80A, silicone rubber, and polyethylene terephthalate (PET) using a cage implant model in Sprague Dawley rats. The synthetic biomedical polymers were subcutaneously implanted in cages for 14 days. Following explantation of the cages and a 2 week healing period, rats were implanted with cages containing the biomedical polymers for an additional 2 weeks. The cellular exudates within the cages were analyzed 4, 7, and 14 days post primary and secondary implantation by flow cytometry for the following cell types: T cells (inclusive of CD8+, CD4+, and CD4+/CD25+ subsets), B cells, granulocytes, and macrophages. At day 14 following secondary implantation, there was an increase in T cells, granulocytes, and macrophages in the exudates compared to primary implantation for all groups inclusive of the empty cage control. However, CD4+/CD8+ ratios, the percentage of CD4+CD25+ T cells, and the macrophage surface adhesion/fusion did not vary significantly upon secondary implantation. Despite a quantitative increase in T cells following secondary