Immune complex trapping in primate spleens. Spleens from untreated primates were stained with PAP in vitro in the presence (a and b) or absence (c and d) of 10% fresh human serum and stained with FITC anti-CD20 Ab’s (green) and TSA-rhodamine (red) to develop PAP. In other studies, primates were injected with 25 mg/kg of PAP 24 hours before sacrifice. Spleen sections from these animals were stained with TSA-rhodamine (red) to develop endogenous peroxidase from the PAP and stained with FITC anti-CD20 Ab’s (e, f, i) to identify mantle area and FITC anti-CD35 Ab’s (g, h, j) to identify FDC networks. Representative spleens from three animals were examined by fluorescence microscopy and photographed at ×100 (a–h) or ×200 (i and j).