Adsorbed endotoxin mediates differential effects on particle-induced stimulation of cytokine and chemokine release [orthopedic implants]

Studies have demonstrated the capacity of metal wear particles from orthopaedic implants to stimulate the release of a variety of pro-inflammatory products. Little is known, however, concerning the mechanisms by which particle attachment and internalization lead to cell activation. Among the factors that influence reactivity are the intrinsic physical chemical properties of the particulate species but also the capacity of the particles to bind serum factors and to present them to cells. The cell responses are then transduced via interactions between these factors (opsonins) and specific cell surface receptors. Ragab et al. (1998) have recently reported that adsorbed bacterial endotoxin is the major factor responsible for activation of cells by titanium metal particles. In the present studies the authors confirm these observations and further investigate the differential capacity of particles to bind endotoxin and induce distinct patterns of cytokine and chemokine responses.