Cobalt-chromium-molybdenum but not titanium-6aluminium-4vanadium alloy discs inhibit human T cell activation in vitro.

This study describes the effect of the presence of cobalt-chromium-molybdenum (CoCrMo) and titanium-6aluminium-4vanadium (Ti6AL4V) disc samples on the CD3-mediated in vitro response of human peripheral blood T lymphocytes. Lymphocyte proliferation in the presence and absence of these metal alloy discs was measured by [3H]thymidine incorporation. Inhibition of lymphocyte proliferation was observed in the presence of CoCrMo disc samples. In contrast, the presence of the Ti6AL4V metal alloy discs had no effect on T cell proliferation. Ultrastructural studies using scanning electron microscopy revealed that the differences in the number of blast cells on uncoated CoCrMo and Ti6AL4V discs from a 4 day culture were consistent with the results observed in the proliferation experiments, i.e. fewer blast cells were seen on the CoCrMo than on the Ti6AL4V discs. In addition, a quantitative analysis of trace elements using total reflection X-ray fluorescence spectrometry in supernatants from 68 h in vitro cultures containing Ti6AL4V or CoCrMo disc samples was performed, revealing differences in the relative metal concentrations in the culture conditions tested. These differences point to the presence of cobalt in the supernatants as a possible determining factor of the inhibition observed. Because cell viability did not appear to change, a more complex mechanism involving the interaction of metals with T lymphocytes may account for the results obtained.