Expression of a soluble form of CTLA4 on macrophage and its biological activity

Interaction between cytotoxic T lymphocyte-associated antigen-4 (CTLA4, CD152) and B7 molecules (B7-1 and B7-2) is of importance in the cellular events of lymphocyte, including antigen-specific T-cell activation and induction of autoreactive T-cell. We describe here the first introduction of a murine soluble CTLA4 gene, CTLA4Ig, to Mm1 cells, a macrophagic cell line. CTLA4Ig was successfully expressed on Mml cells and the expressed CTLA4Ig was found to be functionally active in their binding to B7 molecules by flow cytometry and immunofluorescence studies. The biological activity of CTLA4Ig from the transfected Mm1 cells was studied and showed inhibitory activity on mixed lymphocyte culture. A high CTLA4Ig producing macrophagic cell line was obtained. As Mm1 cells were regarded as difficult for gene transfection and there had so far been no report on expression of CTLA4Ig gene on Mm1 cells, these results suggested that the CTLA4Ig expressing Mm1 cells could be useful for analysis of CTLA4 and B7 molecule interaction in both macrophage and T-cell.