LoVo colon adenocarcinoma cells endogenously express disulfide linked HAI-2 oligomers. Lysates of colorectal adenocarcinoma cells HT29 (A) and LoVo (B) were analyzed by immunoblot for HAI-2 species using the mAb XY9 under 3 different conditions: 1) non-reducing and non-boiled condition (NRNB, lanes 1), 2) non-reducing and boiled condition (NRB, lanes 2), and reducing and boiled condition (RB, lanes 3). The monomer and oligomer forms of HAI-2 are indicated. Two putative enzyme–inhibitor complexes of HAI-2 with an as yet unidentified protease(s) are indicated by ^*, which disappeared when the samples underwent boiling treatment (lanes 2).