Effects of phosphate-based glasses on T lymphocytes in vitro

Host responses to implanted materials can lead to the production of inflammatory mediators and thereby induce potentially adverse reactions, including the activation of T lymphocytes. Although such cells are a central component of immune reactions and likely to be fundamental in determining the long-term clinical efficacy of implants, their response to biomaterials is not well known. This study has therefore examined the in vitro effects of phosphate-based glasses (PG), which can be produced with pre-determined solubility and may be promising materials for promoting the regeneration of new bone and other tissues. Extracts of PG which were modified by the addition of Ca, Co, Zn, and Fe oxides were found to cause only very low levels of activation of human peripheral blood T lymphocytes over a period of 6 days, as measured by changes in DNA synthesis. In contrast, the activation of these cells by concanavalin A, a potent T cell mitogen, was partially inhibited by extracts of a high-Ca PG and nearly totally ablated by the Co-derived extract. These studies show that, despite their apparent inability to activate immunologically responsive cells directly, substances which leach out of metal-containing PG implant materials have the potential to modulate inflammatory reactions.