Prevalence and biological effects of anti-trophoblast and anti-endothelial cell antibodies in patients with recurrent spontaneous abortions

Antibodies: The major participants in maternal-fetal interaction

The aim of this study is to improve our understanding of the mechanisms involved in maternal-fetal immune tolerance. We searched the related literatures and overviewed the major antibodies associated with pregnancy and described in details their possible roles in mediating maternal-fetal interactions. Antibodies classified into different types based on their functional or structural characteristics were summarized, including immunoglobulin G, blocking antibody, nonprecipitating asymmetric antibody, antiphospholipid antibody, antitrophoblast antibody and antipaternal antibody. The presence and levels of various circulating antibodies in pregnancy may play a crucial role in the occurrence, development and termination of pregnancy.

Effects of polyvalent immunoglobulins in patients with recurrent pregnancy loss and antibodies to the choriocarcinoma cell line JEG-3

OBJECTIVE

The benefit of polyvalent immunoglobulins (IVIG) for patients with recurrent pregnancy loss (RPL) is controversially discussed. Anti-trophoblast antibodies as an expression of immune pathology have been associated with RPL. We investigated whether the antibody activity against the choriocarcinoma cell line JEG-3 in RPL patients is influenced in vitro by IVIG.

STUDY DESIGN

Sera of 110 unexplained RPL patients with positive anti-JEG-3 antibodies were coincubated with IVIG in different concentrations (10mg/ml, 20mg/ml, 40mg/ml). Coincubation with human albumin in identical concentrations served as control. Anti-JEG-3 reactivity was measured by using flow cytometry in comparisons with two in-house standards antibody probes of low and high reactivity as described before. Anti-JEG-3 reactivity above the 95% confidence interval of controls was defined as positive.

RESULTS

Incubating RPL sera with 10mg/ml IVIG significantly decreased anti-JEG-3 activity (p<0.001). Increasing IVIG concentration to 40mg/ml resulted in a slightly additionally reduction (p=0.42). In contrast, coincubation with albumin in identically concentrations did not affect anti-JEG-3 activity (p>0.40).

CONCLUSION

Coincubation with IVIG in vitro leads to a significant suppression of anti-JEG-3 activity in the sera of RPL patients.

The complement system in the pathophysiology of pregnancy

A fully active complement system deriving from the maternal circulation as well as from local production by various cell source is present in the placenta. The role of this system at the placental level, as in any other tissue in the body, is to protect both the fetus and the mother against infectious and other toxic agents. As fetal tissues are semi-allogeneic and alloantibodies commonly develop in the mother, the placenta is potentially subject to complement-mediated immune attack at the feto-maternal interface with the potential risk of fetal loss. Uncontrolled complement activation is prevented in successful pregnancy by the three regulatory proteins DAF, MCP and CD59 positioned on the surface of trophoblasts. The critical role played by these complement regulators is supported by the embryonic lethality observed in mice deficient in the complement regulator Crry. Excessive complement activation in the placenta places the fetus at risk for growth restriction or death. The role played by the complement system in the fetal damage induced by anti-phospholipid antibodies in a mouse model will be examined.

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 immunoglobulin G (IgG) treatment of recurrent spontaneous abortion (RSA). The effect in vitro of a commercially available intravenous immunoglobulin (IvIg) on the rate of interleukin (IL)-10 and IL-12 positive cells (Th1/Th2 balance) and on natural killer (NK) cell activity in populations of peripheral lymphocytes of healthy pregnant women and women at risk for premature pregnancy termination was studied. Primary habitual aborters as well as women showing clinical symptoms (bleeding or regular uterine contractions) of threatened premature pregnancy termination were included.

METHODS

Lymphocytes of 20 pregnant women were tested. Five different batches of an IvIg with reported immunomodulatory potential were used at a concentration of 10 mg/mL. Cytokine profiles of the lymphocytes were determined by immunocytochemistry. For testing of NK cell activity, the 4 hr single cell cytotoxicity assay was used.

RESULTS

Incubation with IgG of lymphocytes from recurrent spontaneous aborters concomitantly and significantly decreased the rate of IL-12 positive cells (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, 30 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 activity of normal pregnancy lymphocytes was not altered.

CONCLUSION

This study suggests that incubation of peripheral lymphocytes from RSA patients with polyclonal polyspecific IgG alters cytokine profiles and NK activity while the same treatment does not affect lymphocytes of healthy pregnant women. These data might add to the understanding of mechanisms of action of IvIg in prevention of recurrent pregnancy loss.