DISTRIBUTION OF COLLOIDAL GOLD TRACER WITHIN RAT PARASTERNAL LYMPH-NODES AFTER INTRAPLEURAL INJECTION

Background: Tracer studies are an important tool to obtain information about the processes involved in the immunological response. Colloidal gold is widely used as a tracer, but its small size of label can caus e some difficulty during low-resolution analysis. To overcome this dif ficulty, we developed a new method to follow the route of tracer movem ent within lymph nodes. Methods: We applied conventional X-ray analysi s, X-ray fluorescence analysis (XFA) subtractional microscopy using sy nchrotron radiation (SR) beams, light mycroscopy, and ultrastructural analysis to study the distribution and quantity of colloidal gold coup led with albumin within rat parasternal lymph node 2, 4, 6, 8, and 10 h after intrapleural injection of the tracer. Results: At all the time points XFA-SR revealed that tracer formed a circle with a maximum con centration in the node periphery. XFA-SR measured colloidal gold conce ntration in the nodes reached its maximum (0.5-0.75 weight %) in 6-8 h . Substractional microscopy revealed superficially located groups of c ells filled with colloidal gold tracer. Light microscopy and ultrastru ctural analysis confirmed that the tracer was concentrated in the reti cular cells, situated in the sinuses of the node. Sinusoidal reticular cells concentrated tracer at much higher rates than sinusoidal macrop hages. Four hours after injection, gold appeared in the lysosmes of th e follicular reticular cells. At the same time point, evidence of anti gen presentation was obtained. Antigen presentation proved to be an ex tremely rare event since only one ultrastructural incident was found i n 150 analysed grids. Conclusion: SR is a valuable tool for the analys is of gold tracer passage within the living organism. (C) 1995 Wiley-L iss, Inc.