IFNG and asthma: Another meta-analysis by Lin et al. (21) found that probiotics reduced the frequency of asthma exacerbation, decreased interleukin-4 (IL-4) levels, and increased those of interferon-γ (IFN-γ), but did not significantly affect CACT scores, daytime or nighttime asthma symptoms, FEV1, or peak expiratory flow (PEF).