In contrast, macrophages infected with ΔatsR (herein T6SS+), lacking a negative regulator that results in the overexpression of the T6SS [24], showed higher levels of IL-1β secretion than those infected with the parental MH1K, while infection with ΔT4SS-2 does not affect IL-1β secretion (data not shown). Here, IL1B is linked to infection.