INDUCTION OF T-CELL PROLIFERATION BY RECOMBINANT MOUSE AND CHIMERIC MOUSE HUMAN ANTI-CD3 MONOCLONAL-ANTIBODIES

The isotype of anti-CD3 mAb has a dramatic effect on anti-CD3 induced T-cell activation, as was previously reported for switch variants (IgG2b to IgA) of a high-avidity IgG1 anti-CD3 mAb (CLB-T3/4.1). In order to study and compare the isotype dependency of T-cell activation with anti-CD3 mAb of various mouse and human subclasses, we now prepared recombinant anti-CD3 mAb. The variable region of the anti-CD3 Ig heavy chain was cloned, joined with genes for the heavy chain constant region and expressed in a cell line only secreting autologous mouse kappa-light chains. Thus we obtained cell lines that produced mouse (m) IgM, mIgG3 and chimaeric mouse/human (h) IgM, hIgG1, hIgG2, hIgG3, hIgG4, hIgE and hIgA2 anti-CD3. The matched set of mouse and mouse/human chimaeric anti-CD3 isotype switch variants was then used to study activation of T cells in an accessory cell-dependent system. hIgG1, hIgG4, hIgE, mIgG2a and mIgE induced T-cell proliferation in PBMC of all donors tested, whereas PBMC from a subset of donors were unresponsive to stimulation with hIgG2, hIgG3, hIgA2, mIgG1 and mIgG2b anti-CD3 mAb. hIgM, mIgM and mIgA were only able to induce T-cell mitogenesis in combination with PMA. Our panel of anti-CD3 mAb variants may prove a powerful tool to study mouse and human isotype-dependent effector functions and their influence on T-cell activation requirements in detail.