Uptake of orally administered polystyrene latex and poly(D,L-lactic/glycolic acid) microspheres into intestinal lymphoid tissues in chickens

Fluorescein-labeled microspheres were orally administered to chickens and their distribution in intestinal lymphoid tissues was investigated. Polystyrene latex microspheres were observed in Peyerʹs patches, and also in the Meckelʹs diverticulum and the jejunum. Their density, however, seemed to be lower than that in Peyerʹs patches. Microspheres were rarely observed in the other intestinal tissues examined, including the bursa of Fabricius. Of note is that, although microspheres were present in the lumen, few, if any, were observed in the lamina propria of the caecal tonsil and caecum. Polystyrene latex microspheres of diameter 2.0 μm or 4.5 μm were also observed in Peyerʹs patches, but their density seemed to be lower as compared with the 0.75 μm microspheres. Poly(d,l-lactic/glycolic acid) (PLGA) microspheres were prepared using PLGAs of various molecular weights (MW) and their uptake into Peyerʹs patches was compared. Microspheres prepared with PLGA of average MW of 20 000 were not taken up into Peyerʹs patches, but those prepared with PLGA of average MW of 61 000 or 99 800 were taken up into Peyerʹs patches.