Normal ABO Research Articles

Identification of two novel variants, c.-35A>T and c.[-35A>T, 725T>G], in the FUT1 gene in a patient exhibiting the para-Bombay phenotype.

Reduced or absent H antigens on red cells with the (para-)Bombay phenotype can arise from FUT1 gene mutations, impacting the structure and function of 1,2-L-fucosyltransferase 1 (1,2-L-FucT1). Here, we identified the novel mutations in one patient displaying the para-Bombay phenotype and examined the potential molecular mechanisms underlying this phenotype. ABH antigens and antibodies were detected in patient's blood and saliva using serological methods. The genotypes of ABO, FUT1, and FUT2 were imputed using the genetic variations discovered in the whole exome sequencing data. Three-dimensional (3D) models of FUT1 variants were built using Deepmind's AlphaFold2 and HDOCK, and the possible effects of the variants were predicted to evaluate using DynaMut2 and Polyphen-2. Serological analysis confirmed the para-Bombay B phenotype producing anti-HI and exhibiting normal genotypes ABO*B.01/O.01.02 and FUT2*01.09/01.09. Remarkably, the phenotype is caused by a compound heterozygous genotype: one allele containing the novel c.-35A>T mutation and the known c.725T>G mutation (p.Leu242Arg) of FUT1, and the other allele containing the c.-35A>T mutation. From the computerized stimulation analysis, p.Arg242 of the FUT1 variant may be detrimental, destabilizing, and probably damaging to 1,2-L-FucT1, although not altering the 3D structure of the entire enzyme. The c.-35A>T promoter DNA left at the binding interface of both ZID and c-Rel transcription factors may enable regulation of 1,2-L-FucT1 function at gene promoters. We identified the two novel variants, c.-35A>T and c.[-35A>T, 725T>G], in the FUT1 causing the para-Bombay phenotype. This finding may clarify the molecular mechanisms and enhance blood transfusion safety.

Clinical significance of decreased or loss of ABO blood group expression in acute myeloid leukaemia: A single-centre retrospective study.

Decreased or loss of ABO blood group antigen expression has been observed in acute myeloid leukaemia (AML) patients. We studied the clinical significance of this group in AML patients. This was a retrospective, single-centre cohort study in which the data were retrieved from April 2009 to December 2019. A total of 1592 AML patients with normal ABO blood group antigen (Group I) and 65 patients of decreased or loss of ABO blood group antigen (Group II) group were enrolled. Data were collected at the time of initial admission for pathological diagnosis. To interrogate the underlying mechanism, publicly available The Cancer Genome Atlas AML data were downloaded. Group II consisted of 3.9% (65/1657) of AML patients. The 90-day survival (D90) probability was higher for Group II with a mean survival of 86.4 days compared to 80.6 days for Group I (p = 0.047). Group II had higher haematocrit (28.6 vs. 27.4%) and lower d-dimer, fibrinogen degradation production and C-reactive protein. Publicly available data revealed that among 11 CpG methylation sites within the ABO gene, 4 sites with elevated methylation level were associated with improved D90 survival probability and demonstrated an inverse correlation with ABO gene expression. Lower expression of the ABO gene showed improved survival trends for D90 (p = 0.058) and 180-day survival (p = 0.072). AML with decreased expression or loss of ABO blood group showed better early survival during D90. Transfusion support for this subgroup of AML patients should be meticulously performed considering serum typing.

Genotyping of the rare Para-Bombay blood group in southern Thailand

IntroductionThe para-Bombay phenotype, or H-deficient secretor, results from different mutations of the FUT1, with or without the FUT2 mutation. Consequently, there is an absent or weak expression of the H antigen on red blood cells (RBCs). Routine ABO blood grouping for two siblings with blood group O showed discrepant results with their parental blood group AB. Fragments encompassing the entire coding region of the FUT1 and FUT2 genes were investigated. MethodsBlood and saliva specimens were collected to verify the correct ABO grouping by cell grouping, serum grouping and the hemagglutination inhibition (HI) test, respectively. The FUT1 and FUT2 genomes were identified using the whole-exome sequencing (WES) in two children's DNA blood specimens and may have caused, or been relative to, their blood group. Genetic variations of the FUT1 and FUT2 genes have been investigated in the other family members using the Sanger sequencing. ResultsThe serologic reaction results of the proband revealed that A, B and H antigens were absent on RBCs, and that the serum contained anti-H. However, ABH and AH antigens were present in the saliva PB1 and PB2, respectively. The probands PB1 and PB2 were assigned as AB and A blood groups, respectively. Blood genotyping confirmed that heterozygous mutations of the FUT1 gene, c.551_552delAG, were identified. Three family members, PB3, PB, and PB8, also showed normal ABO blood groups, but their genotypes were also the FUT1 mutation c.551_552delAG. ConclusionsThe FUT1 mutation c.551_552delAG may result in the reduced or absent H antigen production on RBCs, which characterizes the para-Bombay phenotypes. Blood genotyping is essential if these individuals need a blood transfusion or are planning to donate blood.

Two novel alleles on Fucosyltransferase 2 from northern Thai para‐Bombay family and computational prediction on mutation effect

Major characteristics of the para-Bombay phenotype are the absence of ABH antigens on red blood cells due to fucosyltransferase 1 (FUT1) gene mutation and the presence of these antigens in body secretions due to the active fucosyltransferase 2 (FUT2) gene. An ABO blood group discrepancy can be identified via serological testing, and additional tests can be performed for confirmation. This study aimed to resolve the ABO discrepancy and report two novel alleles on the FUT2 gene in northern Thai para-Bombay families. Twelve blood samples were collected from five suspected para-Bombay donors and their families. Nucleotide sequences of ABO, FUT1, and FUT2 were analyzed by polymerase chain reaction-sequence-based typing. Bioinformatics tools were used to predict the effect of suspected novel FUT2 alleles. All samples exhibited normal ABO alleles, concordant with serological test results. FUT1 exhibited three known variants (c.328G>A, c.424C>T, and c.658C>T). Although FUT2 exhibited two known variants (c.357C>T and c.385A>T), two novel alleles were observed. One allele consisted of c.98A>G, c.101T>G, and c.357C>T with predicted normal transferase activity, whereas the other consisted of c.357C>T and c.617T>C with predicted abnormal enzyme activity. Two novel alleles in FUT2 were reported among the affected para-Bombay individuals of northern Thai families. The c.617T>C variant caused an amino acid change from valine to alanine at position 206, predicted to be an inactive FUT2 enzyme. Inheritance of this variant with the recessive FUT1 allele may lead to inheritance of the rare Bombay blood group in the progeny.

Frequency of ABO Blood Group and its Association with Acute Coronary Syndrome in Patients Presenting in a Tertiary Care Center of Nepal

Introduction Coronary artery disease is the major cause of death all over the world. There are studies suggesting association between blood group and coronary artery disease. We attempted to study the frequency of ABO blood group and its association with acute coronary syndrome (ACS) in our hospital.
 MethodsThis is a retrospective, cross sectional study carried out in Manmohan Cardiothoracic Vascular and Transplant Centre from March 2018 to February 2019. Patients who were admitted with diagnosis of ACS were enrolled in the study. Data were recorded and analyzed using SPSS 20. Association between blood group and ACS was analyzed using chi square test and logistic regression.
 ResultsTotal 430 patients were admitted with diagnosis of ACS during the study period, of which 307 (71.4 %) were male and Mean age was 61.22 years (±10.75). Blood group O was the most common type of blood group observed in 207 (48%) patients. ACS was significantly higher in blood group O compared to other groups after adjusting for normal ABO blood group prevalence in general population: blood group O vs. A (OR: 3.45, 95% CI: 2.48- 4.79, p- <0.001), blood group O vs. B (OR: 5.08, 95% CI: 3.53-7.33, p- <0.001), blood group AB vs. O (OR: 0.65, 95% CI: 0.41- 1.02, p- 0.064). Individuals with blood group O and B had increased risk of having STEMI and NSTEMI where as those with blood group A had increased risk of having unstable angina.
 ConclusionThere was association between ABO blood group and coronary artery disease. Individuals with blood group O have increased incidence of ACS.

Frequency of ABO Blood Group and its Association with Acute Coronary Syndrome in Patients Presenting in a Tertiary Care Center of Nepal

Introduction: Coronary artery disease is the major cause of death all over the world. There are studies suggesting association between blood group and coronary artery disease. We attempted to study the frequency of ABO blood group and its association with acute coronary syndrome (ACS) in our hospital. Methods: This is a retrospective, cross sectional study carried out in Manmohan Cardiothoracic Vascular and Transplant Centre from March 2018 to February 2019. Patients who were admitted with diagnosis of ACS were enrolled in the study. Data were recorded and analyzed using SPSS 20. Association between blood group and ACS was analyzed using chi square test and logistic regression. Results: Total 430 patients were admitted with diagnosis of ACS during the study period, of which 307 (71.4 %) were male and Mean age was 61.22 years (±10.75). Blood group O was the most common type of blood group observed in 207 (48%) patients. ACS was significantly higher in blood group O compared to other groups after adjusting for normal ABO blood group prevalence in general population: blood group O vs. A (OR: 3.45, 95% CI: 2.48- 4.79, p- <0.001), blood group O vs. B (OR: 5.08, 95% CI: 3.53-7.33, p- <0.001), blood group AB vs. O (OR: 0.65, 95% CI: 0.41- 1.02, p- 0.064). Individuals with blood group O and B had increased risk of having STEMI and NSTEMI whereas those with blood group A had increased risk of having unstable angina. Conclusion: There was association between ABO blood group and coronary artery disease. Individuals with blood group O have increased incidence of ACS.

ABO antigen levels on platelets of normal and variant ABO blood group individuals

Although differential expression of ABO antigens on platelets is related to recipients’ platelet recovery and neonatal alloimmune thrombocytopenia in ABO-incompatible transfusion and pregnancy, the expression of ABO antigens on platelets in normal and variant ABO blood group individuals is rarely reported. Here, we analyzed the expression of ABO antigens on platelets in a cohort of 515 individuals with normal and variant ABO. The variants were also genotyped for ABO and/or FUT1 loci to distinguish inherited or acquired ABO variants. The results showed that ABO antigens expression on individual platelets was relatively stable during the storage period in vitro. The frequency of low-, moderate-, and high-expression phenotype in normal individual was 59.6%, 35.5%, and 4.9%, respectively. The platelets from para-Bombay and most inherited ABO subgroups express very low levels of ABO antigens, but the acquired ABO variants and the B3 subgroup express normal or abnormally high levels of ABO antigens on platelets. The data extend the information of antigens expression on platelets, which may help to improve the strategy of platelets transfusion.

Comparison of Weak ABO Antigen and Normal ABO Antigen in Patients with Acute Leukemia

To compare the differences between weak ABO antigen patients and normal ABO antigen patients with acute leukemia, and to explore the clinical significance of weak ABO antigen in acute leukemia. The ABO blood group was detected in 110 newly diagnosed acute leukemia patients(including 68 cases of AML and 42 cases of ALL) and 68 normal controls. Then the leukemia subtype, age, sex, laboratory test, risk status of leukemia patients, and DNA methylation of ABO promoter were compared between patients with weak and normal ABO antigen. The weak ABO antigen was found in patients with newly diagnosed acute leukemia, and was not found in ALL patients or normal group. No statistical differences were found in the distribution of ABO blood group, age, hepatosplenomegaly, lymphadenovarix, plt, precursor cell clusters derived from bone marrow, immunopheno-typing, LDH level, and risk status between AL patients of weak and normal ABO antigen groups (P>0.05). Compared with patients in normal ABO antigen group, the pateins in weak ABO antigen group had higher percentage of male(77.8% vs 30%), lower WBC(32.26×109/L vs 82.69×109/L) and Hb level(64.00 g/L vs 85.94 g/L) and higher DNA methylation level (18.91% vs 10.76%) (P<0.05). The cases of weak ABO antigen frequently appear in the male AML patients, the DNA methylation level of ABO gene promoter in patients with weak ABO antigen is significantly higher than that in patients with normal ABO antigen.

Incompatible Crossmatch with Bombay Phenotype (Oh) - A Case Report

Blood serology plays a vital role in transfusion medicine. Presence of an irregular antibody (anti H) in the plasma reacting with all the red cells exhibiting the normal red cell ABO phenotype, the h/h (Bombay) phenotype. The h/h phenotype also known as Oh or Bombay blood group is a rare blood type. It was first discovered in Bombay (Mumbai) in India by Dr.Y.G. Bhende et al in 19521 Generally present in about 4 per million of the human population, though in some places such as Mumbai (Bombay) locals can have occurrences in as much as 1 in 10,000 of inhabitants2 It is also very rare in Bangladesh. The first case was reported in 1990 where three sisters in a same family were of 'Bombay' phenotype3. A 28-year-old male of Noakhali district was admitted to Apollo Hospitals Dhaka on 21st may 2016 with road traffic accident with pelvic fracture. His ABC and Rh blood group was detected as 0 positive by usual blood grouping test procedure. But his cross match was incompatible with several 0 positive blood units. Though the patient’s blood group phenotype initially mimic normal group 0 type by usual test procedure but became apparent when his serum was tested against group 0 red cells and strong Mediate spin agglutination developed at a thermal range 4° to 37°C. After testing with anti H Lectin, Ulex europaeus having anti H like activity, it was detected as Bombay blood group. Therefore, proper serum grouping using A cell, B cell and 0 cell is necessary to detect this group. Bombay phenotype individual do not express H, A and B antigen on their red cells and secretions but their plasma contains potent anti H, anti A and anti B due to lack H antigen4 Normal 0 group red cells does not have A or B antigen but their membrane expresses abundant H antigen. Anti H of Bombay phenotype serum gives incompatible cross match with all red blood cells of normal ABO phenotype containing H antigen. oh phenotype person can receive only autologous blood or blood from another Bombay blood group donor.5 This patient has received blood from her own sister who was also Bombay phenotype but his other four brothers were normal 0 group. Later on he was transfused with blood from Bombay blood group donor, arranged from “Think Foundation”, Mumbai, India for his orthopedic surgery. Both forward and reverse grouping is important for safe transfusion. If not followed, it may lead to people with Bombay blood group, not being detected and categorized as 0 group. Therefore, proper reverse grouping is necessary to detect this group and cross matching at different thermal range also plays a vital role in transfusion safety.Pulse Vol.9 January-December 2016 p.54-59

ABO (histo) blood group phenotype development and human reproduction as they relate to ancestral IgM formation: A hypothesis

The formation of a histo (blood) group) ABO phenotype and the exclusion of an autoreactive IgM or isoagglutinin activity arise apparently in identical glycosylation of complementary domains on cell surfaces and plasma proteins. The fundamental O-glycan emptiness of the circulating IgM, which during the neonatal amino acid sequencing of the variable regions is exerting germline-specific O-GalNAc glycan-reactive serine/threonine residues that in the plasma of the adult human blood group O individuals apparently remain associated with the open glycosidic sites on the ABOH convertible red cell surface, must raise suggestions on a transient expression of developmental glycans, which have been “lost” over the course of maturation. In fact, while the mammalian non-somatic, embryogenic stem cell (ESC)- germ cell (GC) transformation is characterized by a transient and genetically as-yet-undefined trans-species-functional O-GalNAc glycan expression, in the C57BL/10 mouse such expression was potentially identified in growth-dependent, blood group A-like GalNAc glycan-bearing, ovarian glycolipids complementary with the syngeneic anti-A reactive IgM, which does not appear in early ovariectomized animals. This non-somatically encoded, polyreactive, ancestral IgM molecule has not undergone clonal selection and does primarily not differentiate between self and non-self and might, due to amino acid hydroxyl groups, highly suggest substrate competition with subsequent O-glycosylations in ongoing ESC-GC transformations and affecting GC maturation. However, the membrane-bound somatic N/O-glycotransferases, which initiate, after formation of the zygote, the complex construction of the human ABO phenotypes in the trans cisternae of the Golgi apparatus, are associated and/or completed with soluble enzyme versions exerting identical specificities in plasma and likely competing vice versa by glycosylation of neonatal IgM amino acids, where they suggest to accomplish the clearance of anti-A autoreactivity at germline serine and threonine residues. Sustaining the lineage-maintaining position of the classic A allele and the discovery of the OA hybrid alleles at the normal ABO locus and in heterozygous ESC lines have, together with clinical observations, raised discussions about a silent A-allelic support within blood group O reproduction. However, the question of whether a fictional “continued blood group O inbreeding” ultimately occurs without the A-allelic or somatic function remains unanswered because the genetic relationship between non-somatic O-GalNAc-glycosylations that operate before sperm-egg recognition and somatic O-GalNAc-glycosylations that arise after the formation of the zygote remains to be elucidated.

Understanding thread properties for red blood cell antigen assays: weak ABO blood typing.

"Thread-based microfluidics" research has so far focused on utilizing and manipulating the wicking properties of threads to form controllable microfluidic channels. In this study we aim to understand the separation properties of threads, which are important to their microfluidic detection applications for blood analysis. Confocal microscopy was utilized to investigate the effect of the microscale surface morphologies of fibers on the thread's separation efficiency of red blood cells. We demonstrated the remarkably different separation properties of threads made using silk and cotton fibers. Thread separation properties dominate the clarity of blood typing assays of the ABO groups and some of their weak subgroups (Ax and A3). The microfluidic thread-based analytical devices (μTADs) designed in this work were used to accurately type different blood samples, including 89 normal ABO and 6 weak A subgroups. By selecting thread with the right surface morphology, we were able to build μTADs capable of providing rapid and accurate typing of the weak blood groups with high clarity.

Frequency Distribution of ABO Blood Group and Rh Factor among the Local Domiciles of East Midnapore District, West Bengal

Since the discovery of ABO blood group system by Landsteiner a voluminous data is available on the frequencies of ABO blood group and also Rh factor for most parts of the world but such type of data among the localites of East Midnapur is still lacking. The present study is undertaken to find out the normal ABO and Rh frequencies among the localites of East Midnapore.

Aberrant intracellular trafficking of a variant B glycosyltransferase

Little is known about the mechanism by which amino acid polymorphisms outside the catalytically active cleft of ABO glycosyltransferases cause weak ABO phenotypes. Extensive ABO phenotyping and genotyping were performed to classify the blood of a healthy blood group O donor with weak isoagglutinins. ABO antigen and glycosyltransferase expression profiles were then studied in eukaryotic transfection experiments, and the topology of ABO glycosyltransferase was analyzed. The donor's red blood cells were retyped as A(weak), and his serum contained weakly reactive anti-A and anti-B. Sequence analysis revealed two novel ABO alleles. A donor splice-site mutation detected at the exon 6/intron 6 junction of an ABO*A101 allele was predicted to result in skipping exon 6 in the mRNA. The other haplotype displayed a single 688G>C substitution predicting a Gly230Arg exchange in the catalytic domain in an otherwise normal ABO*B101 allele. The transfection studies revealed very weak expression of B antigen by the novel ABO*B allele. According to the topologic analysis, steric hindrance due to the Gly230Arg exchange may cause conformational changes in the variant B transferase. Compared to the wild-type B transferase, the transfected cells exhibited lower-level protein expression and intracellular dislocation. This study provides first evidence that aberrant trafficking of variant ABO transferases may be involved in the formation of weak ABO phenotypes.

An Ael Allele-Specific Nucleotide Insertion at the Blood Group ABO Locus and Its Detection Using a Sequence-Specific Polymerase Chain Reaction

Genomic DNA from each of four Ael, individuals (genotypes AO1, AO1var, AO2) and one AelB individual was used as a template for amplifying exons 6 and 7 of the ABO genes, which were subsequently sequenced. In all the Ael alleles a single nucleotide insertion, compared to the A consensus sequence, was observed that would alter the amino acid sequence of the glycosyltransferase immediately after its postulated nucleotide sugar binding site and furthermore extend the translated protein by 37 amino acids (16 more than the A2 enzyme). A sequence-specific primer PCR assay was developed to detect the nucleotide insertion. It was possible to differentiate all 20 serologically defined Ael/AelB individuals available from 145 blood donors with normal ABO phenotypes and genotypes and 26 individuals with various A subgroups other than A1, A2 and Ael. This mutation explains the Ael phenotype and forms the basis of a method for detecting the Ael allele.

Blood transfusion in the para‐Bombay phenotype

The H-deficient phenotypes found in Chinese so far, have all been secretors of soluble blood group substances in saliva. The corresponding isoagglutinin activity (e.g. anti-B in OB(Hm) persons) has been found to be weak in all cases. To determine the clinical significance of these weak isoagglutinins 51Cr red cell survival tests were performed on three OB(Hm) individuals transfused with small volumes (4 ml) of groups B and O RBC. Rapid destruction of most of the RBC occurred whether or not the isoagglutinins of the OB(Hm) individuals were indirect antiglobulin test (IAGT) reactive. When a larger volume (54 ml packed RBC) of group B cells (weakly incompatible by IAGT) was transfused to another OB(Hm) individual with IAGT active anti-HI, the survival of the transfused RBC was 93% at 24 h, with 30% of the RBC remaining in the circulation at 28 d in contrast to 76% as would be expected if the survival was normal. Therefore when whole units of blood of normal ABO blood groups, compatible by IAGT, are transfused, the survival is expected to be almost normal. These weak isoagglutinins may not be very clinically significant and we suggest that when para-Bombay blood is not available, the compatibility testing for OA(Hm) persons should be performed with group A and group O packed RBC; OB(Hm) with group B and group O packed RBC: OAB(Hm) with groups A, B, AB and O packed RBC. For cross matching, the indirect antiglobulin test by a prewarmed technique should be used.

Mosaicism of red cell ABO type without recognizable cause

A 19 year old woman has been found whose red cells are a mixture of groups A 1B (60%) and A 1 (40%). Tests for many other genetic markers show no other evidence of mosaicism. She is not a twin and her parents and a sib are of normal ABO type. The cause of her dual population of red cells cannot be established, but may be an effect of somatic crossing over or mutation.

AB0 Blood Groups and Coronary Heart Disease (CHD)

The view based on epidemiological and laboratory data that blood group A subjects (=A) have clinically significant higher thrombotic potential than blood group 0 subjects (=O), is supported by the present finding of a significantly higher platelet retention in A than 0. The completely normal AB0 distribution found among 71 cases of proven latent CHD, and the disproportionate excess of 0 vs. A in a consecutive series of 191 coronary artery bypass candidates apparently conflict with epidemiological data indicating a higher risk of achieving CHD in A than 0. The conflict may be solved by suggesting a) that the "thrombotic proneness" in A compared with 0 causes a poorer prognosis in CHD among the former, leaving a disproportionate excess of 0 among longterm CHD survivors, and b) that AB0-related factors have had an insignificant, independent impact on the evolution of preclinical coronary artery disease in our 71 men with latent CHD.

Alpha-L-fucosyltransferases in human serum from donors of different ABO, secretor and Lewis blood-group phenotypes.

The presence of α‐l‐fucosyltransferases in human serum of different ABO, secretor and Lewis blood‐group phenotypes was investigated with guanosine diphosphate fucose as the sugar donor and low‐molecular‐weight oligosaccharides, or a macromolecular glycoprotein, as acceptors. In contrast to the α‐2‐l‐fucosyltransferases in human milk, submaxillary glands and stomach mucosa that occur only in ABH secretors, an enzyme that transfers l‐fucose to the C‐2 position of non‐reducing β‐galactosyl residues was found in the serum of all normal ABO donors irrespective of their ABH secretor‐nonsecretor status. The only sera in which the α‐2‐l‐fucosyltransferase was not demonstrable were three examples of the blood group Bombay Oh phenotype and one example of the Bh phenotype. An a‐3‐l‐fucosyltransferase that conveyed L‐fucose to the C‐3 position in N‐acetyl‐d‐glucosamine or d‐glucose occurred in all the sera examined including those from donors of the Bombay Oh and Bh phenotypes. a‐4‐l‐Fucosyltransferase activity was virtually absent from the sera, irrespective of the Lewis blood group of the donors.

A case of Lewis negative "Bombay" blood type.

SummaryA case of a ‘Bombay’, Lewis negative blood type is described. The saliva of the Proposita has apparently failed to cross — react with anti‐Pn XIV serum. Her red cells scored higher titers than red cells of normal ABO phenotypes with a lectins (Ricinus communis) known to possess anti‐Pn XIV specificity.

The relation of the isoagglutinins in pooled plasma to the haemolytic anaemia of burns.

Patients showing red cell loss following severe burns have been considered in two groups, the more severe cases with late haemoglobinuria and the more numerous less severe cases without late haemoglobinuria. Patients who had late haemoglobinuria usually belonged to group A or AB, showed a normal or increased osmotic fragility of red cells, and had received more than three plasma volumes of pooled plasma. It is suggested that this haemolytic anaemia may have been caused by the anti-A isoagglutinins in pooled plasma or serum. Patients showing red cell loss but who had no late haemoglobinuria had a normal ABO group distribution and an increased osmotic resistance of their red cells. It is concluded that this more common type of red cell loss in burns is independent of transfused isoagglutinins. Isoantibodies present in pooled plasma have been investigated. Corresponding antibodies have been demonstrated in the serum of groups A and AB patients transfused with moderate quantities of pooled plasma. The same patients commonly also had a raised erythrocyte sedimentation rate, without there being a clinically important red cell loss.