FIG. 3.

Three-color FACS analysis demonstrates that a population of CD4⁺ cells which coexpress CD25 and CTLA-4 are expanded only in culture from L3-infected mice. Mice were infected s.c. with 50 L3 or 1 × 10⁵ MF of B. pahangi or were given an equal volume of HBSS only. At day 12 p.i., splenocytes from L3-infected, MF-infected, or control mice were cultured with 10 μg B. pahangi Ag per ml for 72 h. Cells were harvested and stained with FITC anti-mouse CD4 MAb, PE anti-mouse CD25 MAb, and APC anti-mouse CTLA-4 MAb. Cells were analyzed by flow cytometry using gates set with isotype-matched control MAb. Panels show the staining profile of an individual mouse from each group. The numbers at the top right-hand corner of each panel indicate the percentage of CD4⁺ cells that coexpress CD25⁺ and CTLA-4⁺. These figures are representative of the responses of five animals per group.