Dipeptidyl peptidase that cleaves off N-terminal dipeptides from proteins having a Pro or Ala residue at position 2 (By similarity). Acts as a key inhibitor of caspase-1-dependent monocyte and macrophage pyroptosis in resting cells by preventing activation of NLRP1 and CARD8 (PubMed:27820798, PubMed:29396289). Sequesters the cleaved C-terminal part of NLRP1 and CARD8, which respectively constitute the active part of the NLRP1 and CARD8 inflammasomes, in a ternary complex, thereby preventing their oligomerization and activation (By similarity). The dipeptidyl peptidase activity is required to suppress NLRP1 and CARD8; however, neither NLRP1 nor CARD8 are bona fide substrates of DPP8, suggesting the existence of substrate(s) required for NLRP1 and CARD8 inhibition (By similarity). Release of an N-terminal dipeptide, Xaa-Yaa-|-Zaa-, from a polypeptide, preferentially when Yaa is Pro, provided Zaa is neither Pro nor hydroxyproline. Inhibited by zinc (By similarity). Inhibited by the serine proteinase inhibitor 4-(2-aminoethyl)benzenesulphonyl fluoride (AEBSF), and by di-isopropylfluorophosphate (By similarity). Specifically inhibited by isoindoline derivatives (By similarity). Inhibited by Val-boroPro (Talabostat, PT-100), a non-selective inhibitor, which triggers pyroptosis in monocytes and macrophages (PubMed:27820798, PubMed:29396289). Homodimer (By similarity). Forms a ternary complex with NLRP1, composed of a DPP8 homodimer, one full-length NLRP1 protein, and one cleaved C-terminus of NLRP1 (NACHT, LRR and PYD domains-containing protein 1, C-terminus) (By similarity). Forms a ternary complex with CARD8, composed of a DPP8 homodimer, one full-length NLRP1 protein, and one cleaved C-terminus of CARD8 (Caspase recruitment domain-containing protein 8, C-terminus) (By similarity). In the ternary complex, only one subunit of the DPP8 homodimer is bound to NLRP1 or CARD8 (By similarity). Belongs to the peptidase S9B family. DPPIV subfamily.