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Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_III | Pages 546 - 546
1 Aug 2008
‘INVESTIGATING THE EFFECTS OF COBALT CHROMIUM NANOPARTICLES ON THE IMMUNE SYSTEM’
Ogunwale B Brewer J Schmidt-Ott A Tabrizi NS Meek RMD
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Introduction: Metal on Metal articulations produce Cobalt Chromium nanoparticles (CoCrNP) which seems to affect the adaptive immune system, as evident from the perivascular infiltrate of lymphocytes & plasma cells found around some implants, and the reduced CD8+ count described with hip resurfacing. We therefore analyzed effects of CoCrNP on Dendritic Cells, T cells & B cells.

Methods: CoCrNP were produced by repetitive short spark discharges between electrodes of prosthetic CoCr alloy. Electron micrography & BET both confirmed nanoparticle size.

Dendritic Cells were cultured from mouse bone marrow and incubated with CoCrNP of varying concentrations, for 24hrs, or lipopolysaccharide as a positive control. Activation status was then characterized by CD40 expression on FACS analysis.

Cells from mouse lymph nodes were incubated with CoCrNP in varying concentrations. At 48hrs, Propidium Iodide (PI) was added & % PI+ve determined on FACS analysis.

Cells from mouse lymph nodes were cultured in medium without phenol red and incubated with ∝CD3, ∝CD3 + CoCrNP, ∝CD3 + ∝CD28 or ∝CD3 + ∝CD28 + CoCrNP. At 48hrs, Almar Blue was added & difference in light absorbance at 570nm & 600nm was then used to determine T cell proliferation at 72hrs.

Cells from lymph nodes of an MD4 mouse (only able to mount a b cell response to Hen egg Lysozyme (HEL)) were incubated with CoCrNP, HEL (positive control) or CoCrNP + HEL. B cell regulation at 48hrs was characterized by CD40 and CD86 expression on FACS analysis.

Results: CoCrNP did not significantly increase CD 40 expression on DCs or Cd 40/ Cd 86 expression on B cells. At subletal concentrations, CoCrNP inhibited ∝CD3 & ∝CD28 dependent T-cell proliferation.

Discussion: CoCrNP reduces both signal 1 & signal 2 dependent T cell proliferation, which may explain the observed reduction in CD 8+ count with hip resurfacing.

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