FIG. 1.

Optimization of flow cytometric conditions for detecting cytokine-secreting CD4⁺ T lymphocytes in rhesus macaques. PBMC were stimulated with the superantigens SEA and SEB (100 ng/ml each) for 6 h in the presence of Brefeldin A (10 μg/ml). Gated CD4⁺ T lymphocytes are shown. The percentage of CD4⁺ T lymphocytes coexpressing CD69 and TNF-α is shown in the right upper quadrant of each plot. (a) Comparison of soluble versus cross-linked antihuman CD28 MAb for costimulation of superantigen (SAg)-stimulated PBMC. Cross-linking was provided by affinity-purified F(ab′)2 fragments of GAM IgG as described in Materials and Methods. (b) Effect of costimulation with MAbs to CD28 and/or CD49d on TNF-α secretion after superantigen stimulation.