SAg-induced T-cell proliferation by HLA-DR⁺ PMN. PMN were cultured for 44 hours in either the absence or presence of 100 U/mL GM-CSF/IFN-γ from a known HLA-DR^low responder (donor 7; , unstimulated; □, GM-CSF/IFN-γ stimulated) and HLA-DR^high responder (donor 2; ▨, unstimulated; ▪, GM-CSF/IFN-γ stimulated). SAg presentation assays were performed by incubating 1 × 10⁵ PMN with 5 × 10⁴ CD4⁺ T lymphocytes in the presence of 1 nmol/L SEA, SEB, SEC1, SEE, or 10 nmol/L TSST-1 for 66 hours. PMN SAg-induced T-cell proliferation is presented as counts per minute (cpm). Values reflect the amount of [³H]TdR incorporated after an 18- to 20-hour pulse and are the mean of triplicate samples ± SD.