Currently, with few exceptions, practitioners of assisted reproduction tend to attribute “unexplained and/or repeated” IVF failure(s), almost exclusively to poor embryo quality, advocating adjusted protocols for ovarian stimulation and/or gamete and embryo preparation as a potential remedy. The idea that having failed IVF, all that it takes to ultimately succeed is to keep trying over and over using the same recipe is over simplistic. There are numerous non-embryologic causes that can be responsible for failed IVF.
Immunologic factors that cause implantation failure:
The implantation process begins six or seven days after fertilization of the egg. At this time, specialized embryonic cells (i.e., trophoblast), which later becomes the placenta, begin growing into the uterine lining. When the trophoblast and the uterine lining interact along with immune cells in the lining, they become involved in a “cross talk” through mutual exchange of hormone-like substances called cytokines. Because of this complex immunologic interplay, the uterus is able to foster the embryo’s successful growth. Thus, from the earliest stage, the trophoblast establishes the very foundation for the nutritional, hormonal and respiratory interchange between mother and baby. In this manner, the interactive process of implantation is not only central to survival in early pregnancy but also to the quality of life after birth.
Considering its importance, it is not surprising that failure of proper function of this immunologic interaction during implantation has been implicated as a cause of recurrent miscarriage, late pregnancy fetal loss, IVF failure, and infertility. A partial list of immunologic factors that may be involved in these situations includes anti-phospholipid antibodies (APA), antithyroid antibodies (ATA), and, perhaps most importantly, activated natural killer cells (NKa). Presently, these immunologic markers can be adequately measured by highly specialized reproductive immunology laboratories through blood samples.
1) Antiphospholipid Antibodies (APA)
A large body of literature has confirmed that patients who experience repeat IVF failures often have increased levels of circulating APAs. Compelling evidence has also demonstrated that women with pelvic endometriosis and unexplained infertility harbor APAs in their blood. Despite the information, the role of APAs in reproductive outcome is still controversial.
2) Natural Killer (NK) Cells
After ovulation and during early pregnancy, NK cells comprise more than 70% of the white blood cell population seen in the uterine lining. NK cells produce a variety of local hormones known as TH-1 cytokines. Uncontrolled, excessive release of TH-1 cytokines is highly toxic to the trophoblast and endometrial cells, leading to their programmed death (apoptosis) and, subsequently to failed implantation. In the following situations these NK cells can become abnormally activated, and thereby produce these TH-1 cytokines:
When both male and female share specific DNA (DQ-alpha) similarities, the presenting problem is usually recurrent pregnancy loss, rather than “infertility”. This is believed to be due to “too much” similarity between the couple’s DNA and the lack of the production of the protective antibodies to foreign antigens, in this case the embryo. IVIG in such cases may be considered to improve implantation and maintenance of the pregnancy.
Activated NK cells (NKa) can spill over from the uterine lining into the peripheral blood where their toxicity can be measured. IVIG therapy, initiated a week prior to embryo transfer, can subdue activated NK cells, thereby reducing the risk of implantation failure.
3) Cytotoxic Lymphocytes (CTLs)
CTLs release “toxins” (perforins and granzymes) and TH-1 cytokines that counter the humoral, TH-2 cytokine response that is a necessary prerequisite for B-cells to produce antibodies. The “toxins” and TH-I cytokines damage or kill the cells that form the outer layers of the embryo’s root system”(i.e.; the trophoblast). By pitting their TH-1 response against the counter-effect of humoral TH-2 cytokines, both CTLs and activated NK-cells (NKa) regulate and control the degree to which the trophoblast (placenta) invades the uterine wall as well as the tolerance and acceptance by the uterus of the foreign fetal “transplant” (allograph). Studies have shown that women who experience recurrent pregnancy losses have significantly raised levels of CTLs, NKa and TH-1 cytokines in their uterine linings as well as in the peripheral blood.
4) Antithyroid Antibodies (ATA)
A relationship has been established between the presence of ATA and reproductive failure, especially recurrent miscarriage. About 50% of women who harbor ATA also test positive for NKa. The risk of implantation failure in ATA positive women appears to be confined to cases where ATAs coexist with NKa positive.
THERAPEUTIC IMMUNOMODULATION
a) Corticosteroid Therapy (Prednisone, Prednisolone and Dexamethasone)
Steroid therapy has become routine practice in most IVF programs and they are believed to act by inhibiting the cellular immune response. We prescribe oral dexamethasone within ten days of initiating ovarian stimulation with gonadotropins, and continuing until the diagnosis of pregnancy, whereupon, in the event of a negative test, the dosage is tapered over a period of seven to ten days, and then discontinued. Pregnant patients continue treatment throughout the first trimester up to 8 weeks of gestation.
b) Heparin/Lovenox and Aspirin
In cases of recurrent pregnancy loss, current evidence suggests improvement in pregnancy outcome with the use of blood thinners (heparin) and baby aspirin in patients with antiphospholipid syndrome (a thrombophiliac disorder). It is common practice to administer this regimen in the presence of other thrombophilias, despite lack of strong medical evidence. Typically, the regimen is started with the first positive pregnancy test and continued until the end of the first trimester. In some cases, treatment is continued throughout pregnancy until the end of the third trimester or birth.
c) Intravenous Immunoglobulin G (IVIG)
Intravenous immunoglobulin (IVIG) is a sterile, highly purified immunoglobulin G (IgG) derived from large pools of human plasma. All units of human plasma used to prepare IVIG are provided by FDA approved blood establishments only (Red Cross) and tested by FDA-licensed serological tests for infectious agents. Aside from screening for hepatitis, HIV and nucleic acid tests, significant viral reduction is achieved by a combination of processes including Cohn fractionation, pH 4 and solvent detergent treatments. The product is stable for 18 months at room temperature and 24 months in the refrigerator.
There are four ways in which IVIG is believed to counter the anti-implantation effects associated with reproductive immunologic deficiencies. First, it is a potent suppressor of activated (toxic) Natural Killer cells (NKa). Second, IVIG reduces the activity of CTLs (activated T-cells), which are major producers of TH1 cytokines (“toxins”) that can damage the early implanting conceptus. Third, IVIG is believed to suppress the ability of B cells to produce damaging auto-antibodies such as APA and antithyroid antibodies (ATA). Fourth, IVIG contains anti-idiotype antibodies that directly counter many of the damaging effects of autoantibodies (antibodies that attack the body’s own cells), such as antiphospholipid antibodies (APA), thereby protecting the early “root system” of the embryo/conceptus from damage.
We recommend IVIG for increased NKa to be administered at least 7 days prior to embryo/blastocyst transfer and repeated at least once when pregnant. The selective use of immunotherapy has, enabled us to achieve successful pregnancy in patients who had previously suffered repeated IVF failures. Many such patients had previously been advised, not to try again with their own eggs. We have reported successful outcomes in such cases.
d) Intralipid treatment
Intralipid is a good source of calories and essential fatty acids for patients requiring parenteral nutrition for extended periods of time and for prevention of essential fatty acid deficiency. It is contraindicated in patients with abnormalities of normal fat metabolism such as hyperlipidemia, lipoid nephrosis or acute pancreatitis especially if lipid levels are elevated.
Intralipid 20%, 1000 ml contains purified soybean oil 200g, purified egg phospholipids 12g, glycerol anhydrous 22g and water 1000ml. Intralipid solution has been shown to suppress NKa in culture systems and has been proposed to improve reproductive outcome in small number of studies. It is still not clinically proven that it improves pregnancy rates or decreases the risk of miscarriage significantly, but the proposed mechanism of action suggests that it may be helpful. Large scale studies are needed to document the clinical outcomes following intralipid treatment.
