EFFECT OF INTRAVENOUS IMMUNOGLOBULIN-G ON NATURAL-KILLER-CELL CYTOTOXICITY IN-VITRO IN WOMEN WITH RECURRENT SPONTANEOUS-ABORTION

Intravenous immunoglobulin (IVIg) has been used to treat women with re current spontaneous abortion (RSA), particularly for women with elevat ed natural killer (NK) cells. We investigated the effect of IVIg on pe ripheral blood NK cell activity in vitro in women with RSA. Cr-51-rele ase assays using K562 in the presence of varying concentrations of IVI g were performed using PBL from 16 women with RSA. Antibody dependent cellular cytotoxicity (ADCC) was evaluated using Daudi cells. Effecter s and targets were preincubated with IVIg. Binding of IVIg to K562 and Daudi was evaluated by flow cytometry. The effect of K562 absorbed IV Ig on NK activity was compared to that of non-absorbed IVIg. NK cytoto xicity and ADCC in the presence of F(ab')(2) fragments were compared w ith those in the presence of intact IVIg. IVIg produced a significant, dose dependent inhibition of NK activity in vitro. Inhibition of NK a ctivity occurred when effecters but not targets were preincubated with IVIg. IVIg binds to K562 and Daudi. IVIg increased ADCC when targets but not effecters were incubated with IVIg. K562 absorbed IVIg produce d more inhibition of NK cytotoxicity than non-absorbed IVIg. Suppressi on of NK cytotoxicity by F(ab')(2) was as effective as that of IVIg. H owever, F(ab')(2) did not increase ADCC. IVIg effectively reduces peri pheral blood NK cytotoxicity in vitro. Inhibition of NK cytotoxicity i s mediated at the effector cell level through the antigen binding port ion of the immunoglobulins. Women with RSA and elevated NK cells may b enefit from IVIg treatment.