EXPRESSION AND FUNCTIONAL-PROPERTIES OF MOUSE B7 BB1 USING A FUSION PROTEIN BETWEEN MOUSE CTLA4 AND HUMAN GAMMA-1/

We report the construction and expression of a fusion protein made fro m the extracellular portion of the mouse CTLA-4 gene and the constant region of human IgG1. This fusion protein behaves like an antibody to mouse B7/BB1, binding to activated B cells and purified dendritic cell s. In addition, we found it to bind to activated T cells. The fusion p rotein interfered with the ability of antigen-pulsed antigen-presentin g cells to induce proliferation of T-cell clones, although the degree of inhibition varied. These findings are discussed in the light of the physiological activation of T cells in secondary lymphoid organs.