Central to making a diagnosis of an immunologic implantation dysfunction (IID) is a need for the appropriate interpretation of Natural Killer Cell Activity (NKa). In this regard, one of the commonest and most serious errors, is interpret the blood concentration of natural killer cells as being relevant. Rather it is the activity (toxicity) of NK cells that matters as mentioned. This activity can best be measured using the blood, K-562 target cell test (the gold standard). and/ or endometrial biopsy for cytokine activity.

With the K-562 test, the most important consideration is the percentage of target cells “killed” in the “native state”. In most cases a level of >10% killing should be regarded with suspicion and >12% overtly abnormal. In addition to reporting the result of the K-562 test, in the “native state” (without adding, Immunoglobulin-G (IVIG) or Intralipid (IL) which many Laboratories erroneously do to try and determine whether either or both of these immune therapies would have a therapeutic benefit or is/are unlikely to be of clinical value. The entire premise upon which this assertion is based, is in my opinion flawed. Clinically such NK cell deactivation can only be significantly affected in vivo as it takes more than a week following infusion to occur. Thus, what happens to the percentage of target cells killed with the K-562 test, by adding IVIG or IL is in my opinion irrelevant

Another way to assess endometrial NKa is by measuring TH-1 and TH-2 cytokines in endometrial tissue derived through biopsy.TH-1 cytokines kill the trophoblast (the root system of the embryo). Thus if is an excess of TH-1 cytokine activity is found with/without a disruption in the TH-1: TH-2 ratio, this points to NK cell activation.

There are basically two causes of immunologic implantation dysfunction (IID), a) Autoimmune (85%) & , b) Alloimmune (15%). The former occurs when the body reacts to its own tissue and the latter (far less common) when the male and female partners share certain genotypic similarities involving DQ alpha and HLA genes. In both cases IID results in rejection of the pregnancy due to uterine Natural Killer (NK) Cell and T-cell activation leading to the release of an excessive amount of TH-1 cytokines. These, “toxins” attack the embryo’s root system (trophoblast), killing the cells and causing implantation to fail.

1. Autoimmune Implantation Dysfunction:

Autoimmune implantation dysfunction, most commonly presents with presumed “infertility” due to such early pregnancy losses that the woman did not even know she was pregnant in the first place. Sometimes there as an early miscarriage. Tests required are: a) blood levels of all IgA, IgG and IgM-related antiphospholipid antibodies (APA’s) directed against six or seven specific phospholipids, b) both antithyroid antibodies (antithyroid and antimicrosomal antibodies), c) a comprehensive reproductive immunophenotype (RIP) and, c) most importantly, assessment of Natural Killer (NK) cell activity (rather than concentration) by measuring by their killing, using the K-562 target cell test and/or endometrial cytokine activity tests.

It is important to recognize that currently there are only about 3 or 4 Reproductive Immunology Reference Laboratories in the U.S.A that, are capable of reliably analyzing the required elements with a sufficient degree of sensitivity and specificity. I use a Reprosource, a laboratory located in Boston,MA.

2. Alloimmune implantation Dysfunction:

Patients with Alloimmune implantation Dysfunction usually present with a history of unexplained (usually repeated) miscarriages or secondary infertility (where the woman conceived initially and thereupon was either unable to conceive again or started having repeated early miscarriages. However, it can also present as “presumed” primary infertility. Alloimmune dysfunction is diagnosed by testing the blood of both the male and female partners for matching DQ alpha genes and NK/CTL activation. It is important to note that any DQ alpha match (partial or complete) will only result in an IID when there both a DQ-alpha/HLA match exists along with NK cell activation. With the exception of cases where both partners have a total (absolute) DQ-alpha match and treatment requires the use of sperm from a non-matching sperm donor, about 90% of cases alloimmune implantation will have a partial match where 1: 2 embryos will match the woman’s DQ-alpha genotype and half will not. In cases of an alloimmune dysfunction (with associated NKa), treatment with IL or IVIG will in my opinion, will not protect against a matching embryo being rejected. It can only clear the NK environment for an embryo that does not match the woman’s DQ-alpha genotype. For this reason, it is my opinion that only 1 embryo should be transferred at a time because, given the fact that 1:2 embryos will match, transferring >1 embryo at a time creates a risk that the matching embryo will evoke a local NKa/’cytokine response that will “muddy the water” for both. Thus, in cases of a “partial” DQ-alpha match I recommend against transferring more than a single embryo at a time.