ANTIGEN-BINDING AND EFFECTOR FUNCTIONS OF A CHIMERIC ANTIBODY WITH A DELETION OF THE CH1 DOMAIN AND NONCOVALENTLY ASSOCIATED KAPPA CHAINS

In a mouse/human chimeric IgG1Ab with a deletion of the C(H)1 domain t he disulfide bridges be-tween H and L chain cannot be formed, although the corresponding cysteine residues are present. We show that the chi chains are non-covalently associated to H chain dimers and that they can dissociate from the H chains. Therefore different populations of A b can be distinguished according to the number of associated chi chain s. Only the molecules with two chi chains can bind to the target cell. Since this Ab was derived from a T cell depleting anti-Thy-1.2 Ab, we can assess the implications of this conformational alteration as to b inding avidity, effector functions and immunosuppression in vivo.