Immunohistochemically Defined Lymphocyte Function-Associated Antigen 1 (LFA-1) on an Adenocarcinoma Cell Line Is a Distinct Molecule from LFA-1 on Leukocytes

Abstract We previously reported that the immunohistochemically defined LFA-1 antigen (LFA-1-like antigen) was expressed on various exocrine tissues uninvolved with tumors in patients with malignant diseases using LFA-1α-specific monoclonal antibodies (mAb) 2F12 and HVS6B6. In this study we investigated differences at the molecular level between LFA-1 on leukocytes and LFA-1-like antigen on MKN45.16, a subline derived from an adenocarcinoma line MKN45 that expresses a high amount of LFA-1-like antigen. LFA-1-like antigen was reactive to mAb 2F12 or HVS6B6, but not to any of the other five different LFA-1α (CD11a)-specific or four LFA-1β (CD18)-specific mAb. mAb 2F12 immunoprecipitated a 200-kDa membrane protein (LFA-1-like antigen) from MKN45.16 cells, whereas it precipitated 180-kDa (LFA-1α) and 95-kDa (LFA-1β) proteins from a monocytic cell line (THP-1) under both nonreducing and reducing conditions. The molecular difference was confirmed further by N -glycanase treatment of the immunoprecipitates. The isoelectric point of LFA-1-like antigen was 6.0, whereas those of LFA-1α and LFA-1β were 6.0 and 4.7, respectively, by two-dimensional gel electrophoresis. Expression of LFA-1α gene on MKN45.16 cells was not detected at the mRNA level by six different sets of LFA-1α-specific oligonucleotides and reverse transcription–polymerase chain reaction. These results indicated that LFA-1-like antigen on an adenocarcinoma cell line was a distinct molecule from LFA-1 on leukocytes.