Natural killer cell activity and cytokine production after in vitro immunoglobulin treatment of lymphocytes derived from pregnant women with or without risk for spontaneous abortion

OBJECTIVE: To investigate the possible mechanism of action effective in imm unoglobulin G (IgG) treatment of recurrent spontaneous abortion (RSA). The effect in vitro of a commercially available intravenous immunoglobulin (IvI g) on the rate of interleukin (IL)-10 and IL-12 positive cells (Th1/Th2 bal ance) and on natural killer (NK) cell activity in populations of peripheral lymphocytes of healthy pregnant women and women at risk for premature preg nancy termination was studied. Primary habitual aborters as well as women s howing clinical symptoms (bleeding or regular uterine contractions) of thre atened premature pregnancy termination were included. METHODS: Lymphocytes of 20 pregnant women were tested. Five different batch es of an IvIg with reported immunomodulatory potential were used at a conce ntration of 10 mg/mL. Cytokine profiles of the lymphocytes were determined by immunocytochemistry. For testing of NK cell activity, the 4 hr single ce ll cytotoxicity assay was used. RESULTS: Incubation with IgG of lymphocytes from recurrent spontaneous abor ters concomitantly and significantly decreased the rate of IL-12 positive c ells (P < 0.01) and increased the rate of IL-10 positive cells (P < 0.01), whereas such treatment had no significant effect on lymphocytes of pregnant women not at risk of abortion. Dialysis or heat treatment (56 degrees C, 3 0 min) of the IgG preparations did not modify the effect. Elevated NK cell activity of women at risk for premature pregnancy termination significantly decreased after IgG incubation of cells in all cases, whereas NK cell acti vity of normal pregnancy lymphocytes was not altered. CONCLUSION: This study suggests that incubation of peripheral lymphocytes f rom RSA patients with polyclonal polyspecific IgG alters cytokine profiles and NK activity while the same treatment does not affect lymphocytes of hea lthy pregnant women. These data might add to the understanding of mechanism s of action of IvIg in prevention of recurrent pregnancy loss.