Investigation of mechanisms influencing the accumulation of ultrasmall superparamagnetic iron oxide particles in lymph nodes.

RATIONALE AND OBJECTIVES

The current study was designed to investigate the lymph node accumulation mechanisms of dextran-coated ultrasmall superparamagnetic iron oxide particles (USPIO) in rats.

METHODS

The iron deposition in the lymph nodes after intravenous administration of USPIO at a dose of 200 mumol Fe/kg was measured in vitro by inductively coupled plasma atomic emission spectrometer in control rats, in rats after depletion of complement C3, after induction of antidextran antibodies, and with prior ligation of afferent lymphatic vessels. The results were correlated with baseline iron concentration and histology.

RESULTS

A significant increase in iron concentration but unequal distribution between central and peripheral nodes occurred after administration of USPIO in rats. Much less accumulation was observed in guinea pigs. In rats, the nodal uptake of USPIO was not impaired by depletion of complement C3 using cobra venom factor. The central lymph nodes (mesenteric nodes) showed significantly more accumulation of iron particles in the presence of antidextran antibodies induced by dextran preimmunization. Afferent lymphatic vessel ligation did not effect iron particle accumulation.

CONCLUSIONS

Accumulation of USPIO in lymph nodes is largely species-dependent but is independent of afferent lymphatic flow and of C3 complement opsonization in plasma. However, regional distribution of particles can be influenced by preimmunization using dextran.