SPECIFIC-INHIBITION OF CD4(-LYMPHOCYTES BY A HYBRID ANTIBODY() T)

T lymphocytes are crucial in the defense against foreign intruders and cancerous growths. Yet, in circumstances such as transplantation or a utoimmunity, T-cell-mediated responses can be detrimental. Inhibition of these deleterious responses is currently achieved by drugs that ind uce general immune suppression. These compounds also impair the patien t's defenses against infections. Strategies are now being sought that induce selective rather than generalized immune unresponsiveness. One such strategy is the ability to inhibit the activation of CD8(+) T lym phocytes. As CD4(+) T lymphocytes similarly participate in graft rejec tion and in autoimmune diseases, we have now developed a reagent to de lete their activity. It comprises CD4 and an anti-MHC class II antibod y. By virtue of the antibody's specificity for MHC class II molecules, this hybrid antibody (Hab) binds to class II molecules, thereby bring ing CD4 accessory molecules to the surface of class II-bearing stimula tor cells where they occupy CD4 binding sites on class II molecules. A s a consequence CD4(+) T cells with specificity to Hab-coated stimulat or cells cannot engage their CD4 molecules and are no longer activated . This Hab technology provides a strategy to offer specific rather tha n generalized immune suppression.