Gene conversion events between GYPB and GYPE abolish expression of the S and s blood group antigens.

BACKGROUND AND OBJECTIVE: The locus specifying the MNS blood group system is composed of three highly homologous genes, glycophorin A (GYPA), B (GYPB) and E (GYPE). While more than 20 hybrid genes between GYPA and GYPB have been identified, no hybrid genes between GYPB and GYPE have been reported so far. We serendipitously identified GYPB-E-B hybrid genes by studying three individuals whose rare S-s- blood phenotype failed to be predicted by our genotyping platform. MATERIALS AND METHODS: Long-range PCR amplification and extended Sanger sequencing were required to identify and characterize these GYPB-E-B hybrid genes. A PCR assay was developed to detect them in individual or pooled gDNA samples. RESULTS: The first S-s- proband appeared to have two silenced GYPB alleles, one harbouring the so-called P2 mutation and one harbouring GYPE Pseudoexon E4 in place of GYPB Exon B4 (GYPB-E-B hybrid). The two other S-s- probands were homozygous or hemizygous for other GYPB-E-B hybrid alleles, which also lack GYPB Exon B4 and thus do not carry the S/s polymorphism. CONCLUSION: The three GYPB-E-B hybrid genes reported here constitute the first evidence of recombination events between GYPB and GYPE. As these GYPB-E-B hybrid genes drive the S-s- blood phenotype, it is important to know they are a limitation for the current blood group genotyping methods, including those performed by commercial platforms.

Immuno-hematological findings in Delayed Hemolytic Transfusion Reaction (DHTR).

Sickle cell disease (SCD) is the most prevalent genetic disorder in France. Many other countries are also affected. Transfusion is still a key treatment for patients suffering from this condition. As a result, SCD patients are much more exposed to transfusions and their risks than the general population. The most feared situation is delayed hemolytic transfusion reaction (DHTR). In certain situations, defined as hyperhemolysis, autologous red blood cells (RBCs) are also targeted and destroyed. This can put the patient in a life-threating situation. Further transfusions worsen the hemolysis. As DHTR will mimic a new or resistant vaso-occlusive crisis, it can be easily underdiagnosed. SCD patients are more likely to be alloimmunized than the general population, due to discrepancies between the recipient's and donor's RBCs phenotypes. Furthermore, they are often transfused in an inflammatory state, and they also frequently harbor partial antigens in the RH system. SCD patients are more prone to develop a new alloantibody than the general population. As a result, patients with DHTR often have complex mixtures of allo and autoantibodies; RH antibodies and those considered as irregular natural antibodies are frequent. Nevertheless, about a third of DHTRs are reported in patients with no previous history of immunization. In addition, a third of SCD patients will not develop an antibody after a DHTR. The evanescence of the antibodies is important. In several studies, DHTRs were reported only in patients who were occasionally transfused. Identifying patients at risk of developing a DHTR is key to managing them properly.

Management of the blood supply for a Jk(a-b-) patient with an anti-Jk3 in preparation for an urgent heart transplant: An illustrative example of a successful international cooperation.

The Kidd blood group system currently comprises two polymorphic and antithetical antigens, Jka and Jkb, and one high-prevalence antigen, Jk3. Jknull individuals do not express any of the Kidd antigens, and are at risk of developing an anti-Jk3 which is known to be dangerous and responsible for acute or delayed hemolytic transfusion reaction. We report a case of an immunized Jknull patient, who was scheduled to undergo a heart transplant. In order to organize his blood provision management, two conference calls were held between the clinical team and the different staff involved in this challenging blood supply. In light of the blood needs, the available resources, and the constraints, a mix of fresh and frozen units were used. As the supply from France was not sufficient, Finland and New Zealand provided the majority of the fresh units. We report here how this international supply chain was organized, including the difficulties that we encountered. Anticipation, communication and flexibility were essential in making this heart transplant possible without needing to transfuse incompatible units.

Parasite load in guinea pig foetus with real time PCR after maternofoetal transmission of Toxoplasma gondii.

Parasite loads of different tissues were assessed in guinea pig foetus after maternal infection. Twelve female guinea pigs were infected with 100 cysts of the 76 K strain of Toxoplasma gondii by the oral route. Inoculation was performed 20 +/- 5 days (G20) or 40 +/- 5 days (G40) after the beginning of gestation. Gestational age was determined by progesterone assay. Maternal and foetal organ samples were taken 60 days after the beginning of gestation. Parasite loads (from placenta, amniotic fluid (AF), cord blood (CB), foetal brain, liver, lung and spleen) were assessed by a real-time PCR quantification using fluorescence resonance energy transfer (FRET) hybridization probes on the Light Cycler. Congenital transmission was proven by the presence of parasites in blood or tissue samples of the foetus in 84.6% (11/13) and 100% (16/16) of cases after inoculation on G20 and G40, respectively. The quantitative analysis of our results after inoculation at G20 and G40 has allowed us to determinate the positive parasitic loads as a function of the origin of the sample and the period of inoculation. The parasite loads expressed as log (parasite/g) were low in AF and CB samples: 1.49 +/- 0.50 and 1.05 +/- 0.10 at G20 and 1.21 +/- 0.36 and 1.20 +/- 0.42 at G40 respectively. In contrast the placenta and the different foetal tissues had higher parasite burdens: 2.89 +/- 0.54 to 5.30 +/- 0.51 at G20 and 2.81 +/- 0.71 to 3.65 +/- 0.59 at G40. All the placentae were positive for parasites even in the two cases with no proven transmission. Real time quantitative PCR using the hybridization probe was a very sensitive and reproducible technique to study the kinetics of congenital toxoplasmosis in the guinea pig model wich is close to that of humans.