RESUMO
ABO antibodies are naturally occurring antibodies. The ABO antibodies found in the Group O individuals include anti-A and anti-B. In Group O individuals, it tends to be predominantly immunoglobulins G (IgG), although immunoglobulins M and IgA components are also present. Infants of Group O mothers are at higher risk for hemolytic disease of the fetus and new-born than those born to mothers with Group A or B because IgG readily cross the placenta. At the same time, abnormal high concentration of ABO antibody in mother can lead to destruction of platelets in neonates and leads to development of neonatal alloimmune thrombocytopenia as human platelets carry detectable quantities of A and B blood group antigens on their surface. Proper and early diagnosis combined with treatment with intravenous immunoglobulins or transfusion with compatible platelets, may be from mother, can save the neonate from bleeding episodes.
RESUMO
A transfusion recipient lacking a high-incidence antigen (HIA) and has corresponding alloantibody pose a problem in providing compatible blood unit. We encountered a patient with an antibody to an HIA that required identification to assess if compatible blood could be organized. A 65-year-old male was posted for coronary artery bypass grafting surgery. His blood specimen collected in EDTA was referred to the blood bank to provide blood for transfusion. The patient, grouped AB RhD+, had an antibody reacting in saline and antiglobulin phases. It agglutinated all the red blood cells (RBCs) of the 11-cell panel and random donors, indicating specificity to an HIA, though one of his siblings was compatible. After ruling out specificity to HIAs such as H, Inb, and INRA (IN5), the specimen was referred to the New York Blood Centre for further work-up. The antibody reacted with examples of red cells lacking HIA, except those with the Emm- phenotype. The patient's RBCs were typed as Emm-. Anti-Emm in the patient appeared to be naturally occurring as there was no history of transfusion. Naturally occurring alloantibody to an HIA, identified as anti-Emm in phenotype Emm-, is rare and the first of its kind to be reported from India. The case was instrumental in recognizing the Emm as the new blood group system assigned with the symbol ISBT042.
RESUMO
Emm is a high incidence red cell antigen with eight previously reported Emm- probands. Anti-Emm appears to be naturally occurring yet responsible for a clinically significant acute hemolytic transfusion reaction. Previous work suggests that Emm is located on a GPI-anchored protein, but the antigenic epitope and genetic basis have been elusive. We investigated samples from a South Asian Indian family with two Emm- brothers by whole genome sequencing (WGS). Additionally, samples from four unrelated Emm- individuals were investigated for variants in the candidate gene. Filtering for homozygous variants found in the Emm- brothers and by gnomAD frequency of < 0.001 resulted in 1818 variants with one of high impact; a 2-bp deletion causing a frameshift and premature stop codon in PIGG [NM_001127178.3:c.2624_2625delTA, p.(Leu875*), rs771819481]. PIGG encodes for a transferase, GPI-ethanolaminephosphate transferase II, which adds ethanolamine phosphate (EtNP) to the second mannose in a GPI-anchor. The four additional unrelated Emm- individuals had various PIGG mutations; deletion of Exons 2-3, deletion of Exons 7-9, insertion/deletion (indel) in Exon 3, and new stop codon in Exon 5. The Emm- phenotype is associated with a rare deficiency of PIGG, potentially defining a new Emm blood group system composed of EtNP bound to mannose, part of the GPI-anchor. The results are consistent with the known PI-linked association of the Emm antigen, and may explain the production of the antibody in the absence of RBC transfusion. Any association with neurologic phenotypes requires further research.
