TNFAIP3 and infection: A20 protein expression was determined by immunoblotting in THP-1 cells after 24 h of infection with the different NTM species and MTB. M. intracellulare and MTB induced the greatest amounts of A20, followed by M. abscessus and M. avium, and least amount of A20 was induced by M. smegmatis (Figure 6D).