FIG. 2.

rmSEB lacks superantigen activity for pig leukocytes. Pig splenic leukocytes were isolated and cultured in the presence of the indicated concentrations of native SEB (nSEB) or rmSEB. After 40 h of culture, supernatants were taken, and porcine gamma interferon (IFN gamma) secretion was determined using an ELISA. It should be noted that no results are shown for 100 μg/ml of native SEB, as such a high concentration of toxin was nearly 100% toxic to pig leukocytes under these culture conditions. Results are presented as mean values (±standard errors of the mean [SEM]) for triplicate determinations. Levels of gamma interferon that were below the 50-ng/ml detection limit for this ELISA were designated nondetectable (ND). This study was performed twice, with similar results.