Cytotoxicity of anti-PP1Pk antibodies and possible relationship with early abortions of p mothers

Treatment with plasma exchange of a pregnant woman with anti-PP1Pk alloimmunization: A case report

The histo-blood group antigens P, P1 and Pk are a closely related set of glycosphingolipid structures expressed by red blood cells and other tissues. None of these three characters is expressed on p cells, a null phenotype that arises in the context of homozygous mutation of the A4GALT gene. Subjects with p phenotype spontaneously develop a natural alloantibody named anti-PP1Pk, which is a mixture of IgG and IgM against P1, P and Pk. While anti-P1 is a weak cold antibody with poor clinical significance, anti-P and anti-Pk antibodies are potent haemolysins responsible for severe hemolytic transfusion reactions. The rare anti-PP1Pk alloantibodies are associated with recurrent spontaneous abortion in the first trimester of gestation. P and Pk antigens are expressed at high levels on the placenta and antibodies directed against both these structures are deleterious to placental trophoblasts. Here we describe the use of plasma exchange (PEX) in a nulliparous 39-year-old woman with anti-PP1Pk antibodies and a history of repeated spontaneous early abortions and hypofertility. The patient underwent apheresis starting from the third week throughout the pregnancy and a healthy child was delivered by cesarean section at 35 WG. The newborn required only phototherapy within a few days of life. We can state that an early treatment with the only PEX has proven to be effective and safe in the management of a fetomaternal P-incompatibility caused by a high anti-PP1Pk titer (256).

A short history of pluripotent stem cells markers

The expression of one or more of a small number of molecules, typically cell surface-associated antigens, or transcription factors, is widely used for identifying pluripotent stem cells (PSCs) or for monitoring their differentiation. However, none of these marker molecules are uniquely expressed by PSCs and all are expressed by stem cells that have lost the ability to differentiate. Consequently, none are indicators of pluripotency, per se. Here we summarize the nature and characteristics of several markers that are in wide use, including the cell surface antigens, stage-specific embryonic antigen (SSEA)-1, SSEA-3, SSEA-4, TRA-1-60, TRA-1-81, GCTM2, and the transcription factors POUF5/OCT4, NANOG, and SOX2, highlighting issues that must be considered when interpreting data about their expression on putative PSCs.

Clinical consequences of the extremely rare anti-PP1Pk isoantibodies in pregnancy: a case series and review of the literature

BACKGROUND

The absence of the red cell antigens P, P1 and P^k , known as 'p', represents an extremely rare red cell phenotype. Individuals with this phenotype spontaneously form anti-PP1P^k isoantibodies, associated with severe haemolytic transfusion reactions, recurrent spontaneous abortion and haemolytic disease of the fetus and newborn (HDFN).

METHODS

We report a series of four successful pregnancies in three women with anti-PP1P^k isoantibodies, one complicated by HDFN, another by intrauterine growth restriction, all managed supportively. We also review the literature regarding the management of pregnancy involving anti-PP1P^k isoimmunization.

RESULTS

The literature surrounding anti-PP1P^k in pregnancy is limited to a very small number of case reports. The majority report management with therapeutic plasma exchange (TPE) with or without intravenous immunoglobulin. The relationship between titre and risk of pregnancy loss remains unclear, though a history of recurrent pregnancy loss appears important. Although a positive cord blood direct antiglobulin test is frequently noted, clinically significant HDFN appears uncommon, though possible.

CONCLUSION

Early initiation of TPE in high risk patients should be strongly considered. If possible, pregnancies should be managed in a high-risk obstetric or maternal fetal medicine service. The fetus should be monitored closely with interval fetal ultrasound and middle cerebral artery peak systolic volume Doppler to screen for fetal anaemia. Timely sourcing of compatible blood products is likely to be highly challenging, and both directed and autologous donation should be contemplated where appropriate. The International Red Cell Donor Panel may also provide access to compatible products.

Unexpected Non-Maternally Derived Anti-PP1Pk in an 11-Week-Old Patient

Alloantibody formation at less than 4 months of age is rare. Most antibodies identified in these patients are maternally derived. Anti-PP1P^k was detected in an 11-week-old infant that was not maternally derived. A multidisciplinary team approach led to appropriate testing, diagnosis, and transfusion management in this critically ill infant.

Treatment with plasmapheresis and intravenous immunoglobulin in pregnancies complicated with anti-PP1 Pk or anti-K immunization: a report of two patients

BACKGROUND AND OBJECTIVES

In addition to anti-D alloantibody, other antibodies such as anti-K antibody and anti-PP1Pk antibody have been reported to cause severe haemolytic disease of the newborn (HDN). HDN caused by anti-K results not only from destruction of red cells but also from suppression of erythropoiesis. Anti-PP1Pk has been associated with abortion early in pregnancy. We report on two patients, one with anti-PP1Pk and the other with anti-K, who were treated with plasmapheresis and intravenous immunoglobulin (IVIG) during pregnancy in an attempt to reduce the plasma antibody levels.

MATERIALS AND METHODS

The patient with anti-PP1Pk had lost all seven previous fetuses in the first trimester and therefore therapy in this patient was started at 8 weeks of gestation. The second patient had been sensitized to the K antigen through blood transfusion and had had two intrauterine fetal deaths at 26 weeks of gestation with signs of hydrops fetalis. Treatment in this patient was started during the 16th week of pregnancy.

RESULTS

As a result of therapy, the antibody titre was reduced in both patients. In the first patient a healthy infant was delivered by Caesarean section at 37 weeks of gestation. The second patient gave birth at 36 weeks of gestation. Neither newborn required exchange transfusion.

CONCLUSION

In our two patients, plasmapheresis combined with IVIG proved successful in the management of fetomaternal incompatibilities where the mechanism of fetal loss differs from the classical anti-D.

Successful Treatment by Double Filtrate Plasmapheresis in a Pregnant Woman With the Rare P Blood Group and a History of Multiple Early Miscarriages

Individuals of P type, a rare blood group, have anti-PP(1)P(k) antibody in their serum, which causes spontaneous abortion in the early stages. We report a patient of p type suffering from multiple spontaneous abortions. We also review previously reported cases from published work. A 36-year-old woman (gravida 2, para 0) was referred to our hospital because of habitual abortion. At the third pregnancy, we started double filtration plasmapheresis (DFPP) from 7 weeks 3 days to remove the antibody. We attained rapid decline in the titer and normal fetal growth. Gradual tapering of the DFPP frequency caused neither a rebound of the titer nor growth retardation. During the course, she experienced only one episode of catheter infection as an adverse effect. At 37 weeks 3 days, after 57 DFPP repetitions, a 2496 g girl was delivered by cesarean section. The infant suffered neither from anemia nor from severe jaundice. A review of previous reports indicates that the titer of the pathogenic antibody should be kept as low as possible from the early gestational stage in P-incompatible habitual abortion cases, otherwise the case typically comes to an unfavorable outcome. Plasma exchanges with fresh plasma potentially induce contamination by either known or unknown pathogens. Such risks are reduced using DFPP because the volume of albumin solution that replaces fresh plasma is less than that by plasma exchange. The present case, along with previous reports, shows that DFPP is an effective therapy for treating P-incompatible pregnancy.

Additional molecular bases of the clinically important p blood group phenotype

BACKGROUND

The purpose of this study was to explore the molecular basis of the p phenotype by analysis of the recently cloned 4-alpha-galactosyltransferase gene responsible for synthesis of Pk (Gb3) antigen.

STUDY DESIGN AND METHODS

Forty samples from individuals of eight different nationalities were investigated by serologic methods and DNA sequencing of the Pk gene.

RESULTS

Ten different Pk-null alleles, of which 6 are novel, were encountered. The 29 Swedes were homozygous for M183K or G187D, with the former as the predominant allele. Three Israelis were homozygous for a single-nucleotide deletion at codon 219 that shifts and truncates the reading frame by 5 amino acids. Two Italians were homozygous for a triplet deletion causing F81del, while an English donor was heterozygous for F81del but also carried another allele with a combined deletion and insertion. A Pole was heterozygous for alleles with either a single-base deletion at codon 257 or a mutation causing S97L. A Norwegian person and a Japanese person were homozygous for single-base insertions causing a premature stop at codon 282 or extension of the protein by 92 residues, respectively. In 2 samples no mutations were detected.

CONCLUSION

The genetic heterogeneity underlying the p phenotype is further emphasized by this study. To date, 11 p-specific mutations have been found in 14 distinct alleles.

The glycosphingolipid composition of the placenta of a blood group P fetus delivered by a blood group Pk1 woman and analysis of the anti-globoside antibodies found in maternal serum

To further define the molecules that may mediate spontaneous abortion due to maternal-fetal blood group incompatibility within the P blood group system, we have examined the fine specificities of maternal antibodies and the glycolipid antigens from the placenta of a P infant born to a Pk1 mother. Maternal antibodies obtained during therapeutic plasmapheresis were analyzed to determine their reactivities with placental glycolipid extracts on thin-layer plates. Second antibodies specific for IgM, IgG, and IgA revealed immunoglobulins of all of these classes strongly reactive with one major placental glycolipid that comigrates with globoside. GC/MS analysis confirmed that the major P-active pentaglycosylceramide of placenta has the same structure as that previously shown for the P antigen of red blood cells: GalNAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc-Cer. Serum antibodies partially purified by affinity chromatography on globoside-octyl-Sepharose specifically recognize glycolipids that contain terminal GalNAc beta 1-3Gal . . . residues and also recognize the same sequence as an internal determinant in some, but not all, glycolipids with extended globoside core regions. Thus, in the blood group P incompatible fetus, the major P antigen present in placenta has the same carbohydrate structure as the P antigen present in fetal and adult erythrocytes and might be a target for the maternal immune system.

Early treatment by plasmapheresis in a woman with multiple abortions and the rare blood group p

Women with the rare blood group p are known to have an increased rate of abortions. The case of a 36-year-old woman is presented who had had 7 spontaneous abortions in the first trimester and no live child. When treated by plasma exchange begun early in pregnancy and continued until the 29th week, she delivered a normal child. Time to begin, amount and length of time necessary to continue plasma exchange in these patients are considered. In addition, the question of which fraction of the anti-PP1Pk could be responsible for abortion is discussed. To our knowledge, this is the first case of a woman of p phenotype with no live children but with multiple abortions treated by this method, which should be seriously considered in similar cases.

Red cell antigens P (globoside) and Luke: identification by monoclonal antibodies defining the murine stage-specific embryonic antigens -3 and -4 (SSEA-3 and SSEA-4)

Two globoseries antigens (antigens borne on carbohydrate chains containing globoside), SSEA-3 and SSEA-4, were found on the red cells of the majority of people, but were absent from cells of rare p and Pk individuals which lack globoside. In addition, SSEA-4 was absent from red cells of Luke(-) individuals which nevertheless express the P antigen (globoside) and SSEA-3. The name LKE is proposed for the red cell antigen detected by the Luke serum and by MC813-70, the monoclonal antibody defining SSEA-4. Among the LKE+ individuals, a few showed relatively weak expression of the antigen and were grouped separately as a LKE weak (LKEw) phenotype. Using MC813-70, the frequencies of the 3 phenotypes LKE+, LKEw and LKE- in an English donor population are 0.914, 0.072 and 0.014, respectively.