Effects of cobalt and chromium ions on lymphocyte migration

A T cell‐mediated hypersensitivity reaction has been reported in some patients with CoCrMo‐based implants. However, the role of cobalt and chromium ions in this reaction remains unclear. The objective of the present study was to analyze the effects of Co²⁺ and Cr³⁺ in culture medium, as well as the effects of culture supernatants of macrophages exposed to Co²⁺ or Cr³⁺, on the migration of lymphocytes. The release of cytokines/chemokines by macrophages exposed to Co²⁺ and Cr³⁺ was also analyzed. The migration of murine lymphocytes was quantified using the Boyden chamber assay and flow cytometry, while cytokine/chemokine release by J774A.1 macrophages was measured by ELISA. Results showed an ion concentration‐dependent increase in TNF‐α and MIP‐1α release and a decrease in MCP‐1 and RANTES release. Migration analysis showed that the presence of Co²⁺ (8 ppm) and Cr³⁺ (100 ppm) in culture medium increased the migration of T lymphocytes, while it had little or no effect on the migration of B lymphocytes, suggesting that Co²⁺ and Cr³⁺ can stimulate the migration of T but not B lymphocytes. Levels of T lymphocyte migration in culture medium containing Co²⁺ or Cr³⁺ were not statistically different from those in culture supernatants of macrophages exposed to Co²⁺ or Cr³⁺, suggesting that the effects of the ions and chemokines were not additive, possibly because of ion interference with the chemokines and/or their cognate receptors. Overall, results suggest that Co²⁺ and Cr³⁺ are capable of stimulating the migration of T (but not B) lymphocytes in the absence of cytokines/chemokines, and could thereby contribute to the accumulation of more T than B lymphocytes in periprosthetic tissues of some patients with CoCrMo‐based implants.