RECOMBINANT HUMAN-IGA EXPRESSED IN INSECT CELLS

IgA serves as the first line of humoral defense at all mucosal surface s and is present in large quantities in serum. To map the sites of int eraction of immune effector molecules with the IgA constant region (C- alpha), we have expressed soluble, chimeric human IgA in insect cells using recombinant baculoviruses. This antibody is correctly assembled into heavy chain/light chain heterodimers, N-glycosylated, and secrete d by the insect cells; further, when coexpressed with a human J chain, the antibodies can assemble into dimers. The recombinant protein is a uthentic by a number of criteria, including antigen-binding, recogniti on by monoclonal antibodies, complement fixation via the alternative p athway, and specific binding to the monocyte IgA Fc receptor. We have also constructed viruses which encode structurally altered IgA heavy c hains. Using one of these variant viruses, we have shown that glycosyl ation of the second domain of C-alpha is required for interaction with the monocyte IgA Fc receptor. This system should prove useful in furt her characterization of the structure-function relationships in human C-alpha.