IFNG and systemic mastocytosis: In the rural survey, there was a weak inverse association between Sm infection and PPD-specific IFN-γ (adjusted GMR [95% CI]: 0.70 [0.50, 0.99], p = .043); however, there were no significant age- and sex-adjusted associations with any other PPD- or TT-specific cytokine or antibody responses (Table 3A).