Inducible accessory function of a macrophage cell line.

Costimulatory molecules in addition to occupancy of the T-cell antigen receptor, are required to induce T-cell proliferation. Previous work suggested that membrane molecules responsible for costimulatory activity were not constitutively expressed on the antigen presenting cell (APC) surface. In the present study, we have identified a cloned macrophage cell line (FLJ2) with inducible APC function. The unactivated FLJ2 line could not induce T-cell proliferation. FLJ2 could present alloantigen, and stimulate proliferation of either a T-cell clone or normal resting T cells following activation with IFN gamma or unexpectedly with lipopolysaccharide (LPS)-Activated FLJ2 cells could be fixed and APC function was preserved. The relevant inducible molecules required for APC function appeared distinct from Ia and IL1. The expression of ICAM-1 and LFA-1 was increased during activation and anti-LFA-1 antibody blocked APC function. This suggests that one important feature of the activation process may be improvement of cellular adhesion.