FIG. 4.

NO production by macrophages exposed to culture supernatants of B. bovis-specific Th-cell lines. NO₂⁻ levels were determined by the Griess assay of culture supernatants from macrophages that were cultured for 96 h with B. bovis-specific T-cell culture supernatants (75%, vol/vol) obtained from C97, G3, and G6 cell lines. Controls consisted of complete RPMI 1640 culture medium or 1,000 U of IFN-γ per ml, and each treatment was performed in the absence (open bars) or presence (solid bars) of 250 μM l-NMMA. Results are shown as the mean NO₂⁻ levels for quadruplicate cultures and 1 SD.