FIG. 5.

FITC-labeled Tc-1 IgG specifically binds to the surface of trypomastigotes. Trypomastigotes were washed with Hanks' balanced salt solution, fixed with 1% paraformaldehyde, and incubated with FITC-labeled Tc-1 IgG, FITC-labeled Tc-1 IgG in the presence of a 100× excess of unlabeled Tc-1 IgG, or FITC-labeled preimmune IgG. (A) FITC-labeled IgG to Tc-1 binds uniformly to the surface of trypomastigotes. (B) Binding of FITC-labeled IgG to Tc-1 is abolished by a 100× excess of unlabeled Tc-1 IgG. (C) FITC-labeled preimmune IgG does not bind to trypomastigotes. A′, B′, and C′ show that trypanosomes were present in the preparations shown in A, B, and C, as seen in their respective light fields. This is a representative experiment of three independent experiments performed with similar results.