ANTIBODIES TO THE CD5 MOLECULE IN NORMAL HUMAN-IMMUNOGLOBULINS FOR THERAPEUTIC USE (INTRAVENOUS IMMUNOGLOBULINS, IVIG)

IVIg are increasingly used for the treatment of autoimmune diseases. I n the present study, we show that IVIg contain antibodies directed aga inst CD5, a cell surface molecule of T cells which is also a marker of the autoantibody-producing CD20+('B-1') subset of B lymphocytes. Anti bodies to the CD5 molecule were demonstrated in IVIg by the ability of therapeutic preparations of IVIg to inhibit the binding of labelled C D5 MoAb to the CD5-expressing human T cell line H9. Preincubation of H 9 cells with IVIg or with F(ab')2 fragments prepared from IVIg resulte d in dose-dependent inhibition of the binding of CD5 antibody. The pre sence in IVIg of antibodies to the CD5 molecule was further confirmed by the binding of IVIg to mouse L cells that expressed human CD5 molec ules following a stable transfection with CD5 cDNA. Human CD5 antibodi es in IVIg provide therapeutic immunoglobulin preparations with the po tential of modulating T cell functions through CD5, and of regulating the expression of B cell subsets expressing CD5. This may have implica tions for the treatment of autoimmune diseases.