Long-term in vivo survival of Rh(D)-negative donor red cells in a patient with anti-LW

A new high-prevalence LW antigen detected by an antibody in an Indigenous Australian homozygous for LW*A c.309C>A variant

BACKGROUND AND OBJECTIVES

The LW gene encodes the LW glycoprotein that carries the antigens of the LW blood group system. LW antigens are distinct from D antigen, however, they are phenotypically related and anti-LW antibodies are often mistaken as anti-D. An antibody was detected in an Australian patient of Aboriginal descent who consistently typed as LW(a+b-). This study aimed to describe the antibody recognizing a high-prevalence antigen on the LW glycoprotein.

STUDY DESIGN AND METHODS

Samples from the patient and her four siblings were investigated. DNA was genotyped by single nucleotide polymorphism (SNP)-microarray and massively parallel sequencing (MPS) platforms. Red blood cells (RBCs) were phenotyped using standard haemagglutination techniques. Antibody investigations were performed using a panel of phenotyped RBCs from adults and cord blood cells.

RESULTS

SNP-microarray and MPS genotyped all family members as LW*A/A, (c.299A), predicting LW(a+b-). In addition, a novel LW*A c.309C>A single nucleotide variant was detected in all family members. The patient and one of her siblings (M4) were LW c.309C>A homozygous. Antibody from the patient reacted positive to all reagent panel RBCs and cord blood cells but negative with RBCs from LW(a-b-), Rh_null and sibling M4. Antibody failed to react with RBCs treated with dithiothreitol.

CONCLUSION

Antibody detected in the patient recognized a novel high-prevalence antigen, LWEM, in the LW blood group system. LWEM-negative patients who developed anti-LWEM can be safely transfused with D+ RBCs, however, D- is preferred. Accurate antibody identification can help better manage allocation of blood products especially when D- RBCs are in short supply.

[A new case of allo-anti-LWab]

A patient admitted to hospital for hip replacement was found incompatible in pretransfusion testing due to allo-anti-LWab antibody, as well as anti-JKb, anti-E and anti-IH antibodies. The patient had a rare phenotype LW(a-b-ab-). The antibodies were acquired though pregnancy and/or transfusion. This newly discovered anti-LWab allowed us to study and emphasize the relevant serological and transfusional aspects related to incompatibility caused by "public" antibodies in association with other alloantibodies. We attempted to update the LW system in the light of Sistonen and Tippett's recent discoveries. We collected the required compatible units of blood through autologous donations and a Central Canadian Red Cross Registry for rare donors.

Transfusion significance of LWa allo-antibodies

An example of anti-LWa, arising as a complication during a RhD immunization programme, has been studied for evidence of its likely in vivo haemolytic properties. In vitro testing of the anti-LWa showed it to be largely IgG1 acting by the antiglobulin technique. Results of antibody-dependent cellular cytotoxicity and macrophage phagocytic assays were both negative. However, 99mTc-labelled Lw(a+) donor cells showed a slight reduction in t1/2 (18 h) compared with the normal survival of autologous cells. Despite this observation, and bearing in mind the difficulties of interpreting apparently accelerated destruction of small serologically incompatible red cells, it was concluded that the presence of this example of anti-LWa should not be a bar to urgent transfusion.

Reduced survival of isotope-labelled Rh(D)-negative donor red cells in a patient with anti-LWab

The serum of an 85-year-old Caucasian male with no history of blood transfusion contained an IgG3 antibody with anti-LWab specificity. The antibody failed to react with dithiothreitol-treated red cells, and there was a marked reduction in titre of the antibody with pronase-treated cells, findings consistent with an antibody having this specificity. High association values were obtained in a mononuclear phagocyte assay when LW-positive red cells, sensitised in vitro with the patient's serum antibody, were incubated with peripheral blood monocytes from the patient. In vivo red cell survival studies demonstrated that 99mTc-labelled rhesus-negative (rr), LW-positive red cells had 53% survival at 1 h. The IgG subclass of the antibody, mononuclear phagocyte assay results and in vivo survival studies predicted a significant reduction in the posttransfusion survival of therapeutic volumes of rhesus-negative (rr), LW-positive red cells.