The microvasculature of the hamster cheek pouch as a model for studying acute immune-complex-induced inflammatory reactions (with 1 color plate).

The acute microvascular reactions induced by immune complexes were studied. Hamster cheek pouch preparations of ovalbumin (OA)-immunized animals were topically exposed to different doses of OA (0.1, 1, 10 or 100 micrograms/ml). Fluorescein-isothiocyanate-labelled dextran (FITC-dextran, molecular weight 150,000) was injected intravenously as a macromolecular tracer. The microvascular alterations observed upon exposure to OA ranged, in a dose dependent way, from a mild vasoconstriction and reversible vascular leakage from postcapillary venules exhibited by 0.1 micrograms/ml OA, to a severe long-lasting vasoconstriction, platelet aggregation, stasis, leukocyte accumulation in venules and prolonged vascular leakage from venules seen after exposure to 100 micrograms/ml OA. Exposure of immunized animals to 100 micrograms/ml fluorescein-labelled OA (FITC-OA) resulted in deposition of FITC-OA at the walls of small venules, indicating immune complex formation at these sites. A more diffuse pattern of FITC-OA localization at venules was seen with 10 micrograms/ml FITC-OA, which may possibly indicate formation of smaller more soluble immune complexes with lower doses of OA. The intravital model used in this study forms a basis for studying immunologically induced acute inflammatory reactions at the microvascular level.