Kell System Antigens Research Articles

Rh and Kell blood group antigen prevalence in a multi-ethnic cohort in Nigeria: implications for local transfusion service

Antigens belonging to the Rh and Kell blood group systems are of major clinical significance because of their immunogenicity and the potential of their consequent antibodies to cause in vivo destruction of exogenous red blood cells (RBCs). Despite the wide-spread use of transfusion, there are sparse data on the prevalence of Rh and Kell system antigens and their ethnic variability in Nigeria. The objective of this study was to determine the prevalence of the five major Rh (D, C, c, E, e) and Kell (K) system antigens in Nigeria with the goal of understanding alloimmunization risk in transfusion recipients and improving transfusion safety through the availability of resources, such as antisera for extended RBC typing and antigen panels for alloantibody detection. A multi-ethnic cohort of 302 healthy Nigerian individuals was created to study RBC antigen prevalence. The antigen status of these individuals for Rh and K antigens was determined using commercially prepared antisera and conventional tube agglutination methods. The prevalence of the Rh antigens in the study cohort was found to be: D (92.7%), C (20.5%), c (97.7%), E (19.5%), and e (97.4%). Dce was the most common Rh phenotype (53.3%). The prevalence of K was 0 percent. For all antigens, there was no association between ethnicity and antigen prevalence. This study is the first to document the prevalence of the major Rh and K antigens in the Nigerian population, using a multi-ethnic cohort. Serologic testing demonstrates a zero prevalence of K antigen, which has never been described. C and E pose the higher risks of alloimmunization, hence showing a need for extended RBC typing and matching in at-risk blood recipients. This study demonstrates that phenotyping for major Rh and K antigens within the Nigerian population can potentially improve transfusion safety and prevent alloimmunization.

Phenotypic Profile of Rh and Kell Blood Group Systems among Blood Donors in Cote d'Ivoire, West Africa.

Few countries in sub-Saharan Africa make systematic searches for antigens C, c, E, and e of the Rh and Kell system antigens in the donor and recipient, thereby exposing transfused patients. Purpose and Objectives. In this paper, we propose to determine the red cell Rh and Kell blood groups among blood donors from traditional techniques to improve medical care of transfused patients. This study will allow us to assess the frequency of blood group antigens in these systems. Study Design and Methods. We carried out a study on the red cell typing in the blood donor population of the National Blood Transfusion Center in Abidjan. This study was performed on 651 blood donors. Results. For the Rh system, the antigen frequencies of D, c, e, C, and E are, respectively, 92.93%, 99.85%, 99.85%, 21.97%, and 13.82%. K antigen is found in 0.77% of donors. Discussion and Conclusion. Although the frequencies of the most immunogenic antigens are lower than in the white race, lack of preventive measures makes the immunological risk high in Africa. Furthermore, Africa is full of specificities that are important to note for a better care of our patients.

Molecular DNA‐based testing for blood group antigens: recipient–donor focus

DNA‐based testing for blood group antigens has become commonplace in a number of clinical situations to improve transfusion therapy for blood transfusion recipients. These include typing for antigens in patients who are multiply transfused to determine which blood group antibodies may be present, typing when the red blood cells (RBCs) are coated with immunoglobulin, and typing for uncommon antigens, especially when no serologic reagent is available. Other clinical applications include resolving ABO typing discrepancies for patients awaiting transplant, or determination of the original type of a bone marrow transplant recipient, or confirmation of an ABO subgroup in a kidney donor. Testing for the specific mutation associated with depressed Kell system antigens in McLeod syndrome may also have value because different mutations appear to be associated with prognosis.Applications in prenatal medicine include discrimination between weak D and partial D to determine if a pregnant woman is a candidate for Rh immune prophylaxis, and assessing the risk for hemolytic disease of the fetus or newborn and neonatal thrombocytopenia. Assessing risk includes testing the paternal sample for the target antigen, and if positive testing for gene copy number (zygosity) and testing the fetus from amniocentesis or non‐invasive maternal plasma sample.Donor centers are now able to screen large numbers of donors to label antigen‐negative RBC products. DNA typing will change transfusion practice by allowing patients facing chronic transfusion therapy to have a more comprehensive blood group antigen profile performed, and to receive donor units antigen‐matched for more than ABO and RhD to reduce alloimmunization. A patient who makes an alloantibody to a RBC antigen is forever at risk for his or her lifetime; for a serious transfusion reaction if ever requiring transfusion in an emergency, and also for a high risk pregnancy if a woman of child bearing age. Prevention of alloimmunization is an important advance in transfusion safety and is now possible with electronic patient medical records and testing and labeling of blood products for additional blood group antigens.

Alloimmunization screening after transfusion of red blood cells in a prospective study

BackgroundSeveral irregular red blood cell alloantibodies, produced by alloimmunization of antigens in transfusions or pregnancies, have clinical importance because they cause hemolysis in the fetus and newborn and in transfused patients.Objectivea prospective analysis of patients treated by the surgical and clinical emergency services of Hospital de Clínicas of the Universidade Federal do Triângulo Mineiro (HC/UFTM), Brazil was performed to correlate alloimmunization to clinical and epidemiological data.MethodsBlood samples of 143 patients with initial negative antibody screening were collected at intervals for up to 15 months after the transfusion of packed red blood cells. Samples were submitted to irregular antibody testing and, when positive, to the identification and serial titration of alloantibodies. The Fisher Exact test and Odds Ratio were employed to compare proportions.ResultsFifteen (10.49%) patients produced antibodies within six months of transfusion. However, for 60% of these individuals, the titers decreased and disappeared by 15 months after transfusion. Anti-K antibodies and alloantibodies against antigens of the Rh system were the most common; the highest titer was 1:32 (anti-K). There was an evident correlation with the number of transfusions.ConclusionsGiven the high incidence of clinically important red blood cell alloantibodies in patients transfused in surgical and clinical emergency services, we suggest that phenotyping and pre-transfusion compatibilization for C, c, E, e (Rh system) and K (Kell system) antigens should be extended to all patients with programmed surgeries or acute clinical events that do not need emergency transfusions.

Alloimmunization to both Rh and Kell system antigens (anti-C and anti-K) in a young thalassemic patient

Alloimmunization to both Rh and Kell system antigens (anti-C and anti-K) in a young thalassemic patient

A Hemolytic Transfusion Reaction due to Anti-Ku Antibody in a Patient with Knull Phenotype: The First Case in Korea

Knull phenotype completely lacks all Kell system antigens. Anti-Ku antibody is seen in immunized persons with Knull phenotype by transfusion or pregnancy. It can cause a fatal hemolytic transfusion reaction. A 66-yr-old male patient with liver cirrhosis visited emergency center due to acute bleeding. The patient was at hypovolemic shock status: his blood pressure was 80/50 mmHg, pulse rate was 110/min and hemoglobin level was 4.4 g/dL. Because of the presence of antibody against high incidence antigen, we could not find any compatible blood for the patient. Nevertheless, 4 units of packed RBCs had to be transfused. Moderate hemolytic transfusion reaction was developed after transfusion. At endoscopic examination, blood was spurting from gastric cardiac varix. Endoscopic histoacryl injection was tried, and bleeding was successfully controlled. After bleeding stopped, he was managed for anemia using steroid and other medical therapy instead of transfusion. His hemoglobin level was improved to 7.7 g/dL at the time of discharge. Later he has been proved to have a Knull phenotype, which is very rare, and anti-Ku antibody. This report is the first case of anti-Ku in a Knull phenotype person in Korea, who experienced a moderate hemolytic transfusion reaction.

Insights into extensive deletions around the XK locus associated with McLeod phenotype and characterization of two novel cases

The McLeod phenotype is derived from various forms of XK gene defects that result in the absence of XK protein, and is defined hematologically by the absence of Kx antigen, weakening of Kell system antigens, and red cell acanthocytosis. Individuals with the McLeod phenotype usually develop late-onset neuromuscular abnormalities known as the McLeod syndrome (MLS). MLS is an X-linked multi-system disorder caused by absence of XK alone, or when the disorder is caused by large deletions, it may be accompanied with Duchenne muscular dystrophy ( DMD), chronic granulomatous disease ( CYBB), retinitis pigmentosa ( RPGR), and ornithine transcarbamylase deficiency ( OTC). XK defects derived from a large deletion at the XK locus (Xp21.1) have not been characterized at the molecular level. In this study, the deletion breakpoints of two novel cases of McLeod phenotype with extensive deletions are reported. Case 1 has greater than 1.12 million base-pairs (mb) deletion around the XK locus with 7 genes affected. Case 2 has greater than 5.65 mb deletion from TCTE1L to DMD encompassing 20 genes. Phylogenetic analyses demonstrated that DMD, XK and CYBB have close paralogs, some of which may partially substitute for the functions of their counterparts. The loci around XK are highly conserved from fish to human; however, the disorders are probably specific to mammals, and may coincide with the translocation of the loci to the X chromosome after the speciation in birds. The non-synonymous to synonymous nucleotide substitution rate ratio ( ω = d N/d S) in these genes was examined. CYBB and RPGR show evidence of positive selection, whereas DMD, XK and OTC are subject to selective constraint.

USE OF RECOMBINANT ERYTHROPOIETIN FOR THE MANAGEMENT OF SEVERE HEMOLYTIC DISEASE OF THE NEWBORN OF A K0 PHENOTYPE MOTHER

Very few people do not express any Kell antigens on their red blood cells (K0 phenotype). They can be immunized by transfusion or pregnancy and develop antibodies against Kell system antigens. These maternal antibodies can cause severe hemolytic disease of the fetus/newborn, as a result of the suppression of erythropoiesis and hemolysis. Multiple intrauterine transfusions in the management of severe hemolytic disease have been shown to cause erythropoietic suppression as well. Recombinant erythropoietin has been successfully used in the management of late anemia of infants with Rh hemolytic disease and in 1 case of KEL1 (Kell)-associated hemolytic disease. The authors present the case of severe hemolytic disease of a newborn due to KEL5 (Ku) isoimmunization of his K0 phenotype mother. Regular intrauterine transfusions were performed to manage the severe fetal anemia (Hb 3 g/dL). A male infant was born at the 36th week of gestation having normal hemoglobin (15.8 g/dL) and developed only mild hyperbilirubinemia. On the 15th day of life, the infant's hematocrit had fallen to 27.3%, with low reticulocyte count and low erythropoietin level. The infant was managed successfully with recombinant erythropoietin.

A KEL gene encoding serine at position 193 of the Kell glycoprotein results in expression of KEL1 antigen

The KEL2/KEL1 (k/K) blood group polymorphism represents 578C>T in the KEL gene and Thr193Met in the Kell glycoprotein. Anti-KEL1 can cause severe hemolytic disease of the fetus and newborn. Molecular genotyping for KEL*1 is routinely used for assessing whether a fetus is at risk. Red blood cells (RBCs) from a KEL:1 blood donor (D1) were found to have abnormal KEL1 expression during evaluation of anti-KEL1 reagents. Kell genotyping methods, including KEL exon 6 direct sequencing, were applied. KEL cDNA from D1 was sequenced. Flow cytometry was used to assess KEL1 and KEL2 RBC expression. RBCs from the donor, her mother, and an unrelated donor gave weak or negative reactions with some anti-KEL1 reagents. Other Kell-system antigens appeared normal. The three individuals were homozygous for KEL C578 (KEL*2) but heterozygous for a 577A>T transversion, encoding Ser193. They appeared to be KEL*2 homozygotes by routine genotyping methods. Flow cytometry revealed weak KEL1 expression and normal KEL2, similar to that of KEL*2 homozygotes. Ser193 in the Kell glycoprotein appears to result in expression of abnormal KEL1, in addition to KEL2. The mutation is not detected by routine Kell genotyping methods and, because of unpredicted KEL1 expression, could lead to a misdiagnosis.

A McLeod phenotype detected by random screening for K:‐4 [Kp(b–)] blood donors in Brazil

The red blood cells of the McLeod phenotype have weak expression of Kell System antigens due to no expression of XK protein. One blood donor reacted as K:-4 [Kp(b-)] during a screening assay. Subsequent serologic studies demonstrated weak expression of K:4 and all other high-incidence Kell system antigens tested; however, no expression of Kx antigen was observed. One apparently healthy blood donor demonstrated low expression of K:2, K:4, K:5, K:7, K:14, K:22, and no Kx antigen in his red blood cells. His brother and mother showed the same weak expression, and his father showed normal expression of antigens tested. Flow cytometry studies confirmed the mother's status as a McLeod carrier female. Genotyping determined the presence of KEL2 and KEL4 alleles in mother and siblings. Southern blot with an exon-1 probe showed fragments shorter than predicted for the siblings and the mother, suggesting a deletion. Polymerase chain reaction with primers spanning exon 1 and flanking regions displayed a similar pattern. Deoxyribonucleic acid sequence allowed the precise characterization of a deletion of 392 bp, beginning at the 5' of the coding region up to nucleotide 201 of exon 1, which putatively abrogates the production of XK protein. Two brothers with McLeod phenotype in a Brazilian blood-donor population were identified. The molecular basis for this phenotype is a 392-bp deletion spanning from 5' of the coding region to exon 1 of the XK gene, never described before.

Point mutations causing the McLeod phenotype.

The McLeod phenotype is defined by absence of Kx, weakening of Kell system antigens, and acanthocytosis. Individuals with the McLeod phenotype usually develop late-onset neuromuscular abnormalities. Gene deletions, insertions, and point mutations that affect RNA splicing or that lead to premature stop codons have been reported to cause the McLeod phenotype. The McLeod phenotype may also be caused by mutations at a different splice site and by a novel mutation encoding an amino acid substitution that prevents transport to the cell surface. The coding and flanking intron regions of XK from four male, unrelated individuals with the McLeod phenotype and non-chronic granulomatous disease were sequenced and compared with the wild type sequence. Genomic DNA was amplified by PCR, and the products were sequenced. In one case, the mutant cDNA was expressed in a heterologous cell, and cell surface expression was determined. Three individuals with the McLeod phenotype had mutations that disrupted conserved GT sequences present at RNA splice sites. Two of them had G>C mutations at the 5' splice site of intron 1, and one had a G>A mutation at the 5' splice site of intron 2. One person with the McLeod phenotype had a 746C>G mutation in exon 3 encoding an R222G substitution. In a transfected cell, the expressed protein from the latter mutant did not travel to the cell surface. The McLeod phenotype may be caused by several different mutations.

Identification of a Defect in the Intracellular Trafficking of a Kell Blood Group Variant

Blood group polymorphisms have been used as tools to study the architecture of the red blood cell (RBC) membrane. Some blood group variants have reduced antigen expression at the cell surface. Understanding the underlying mechanism for this reduced expression can potentially provide structural information and help to elucidate protein trafficking pathways of membrane proteins. The Kp(a+) phenotype is a variant in the Kell blood group system that is associated with a single amino acid substitution (R281W) in the Kell glycoprotein and serologically associated with a weakened expression of other Kell system antigens by an unknown mechanism. We found by immunoblotting of RBCs that the weakening of Kell antigens in this variant is due to a reduced amount of total Kell glycoprotein at the cell surface rather than to the inaccessibility of the antigens to Kell antibodies. Using a heterologous expression system, we demonstrate that the Kpa mutation causes retention of most of the Kell glycoprotein in a pre-Golgi compartment due to differential processing, thereby suggesting aberrant transport of the Kell protein to the cell surface. Furthermore, we demonstrated that single nucleotide substitutions into the coding region of the common KEL allele, as predicted by the molecular genotyping studies, was sufficient to encode three clinically significant low incidence antigens. We found that two low incidence antigens can be expressed on a single Kell protein, thus showing that the historical failure to detect such a variant is not due to structural constraints in the Kell protein. These studies demonstrate the power of studying the molecular mechanisms of blood group variants for elucidating the intracellular transport pathways of membrane proteins and the requirements for cell surface expression.

EDTA/glycine-acid versus chloroquine diphosphate treatment for stripping Bg antigens from red blood cells

EDTA/glycine-acid (EGA) has been reported to remove IgG-bound antibodies from red blood cells (RBCs) and to denature Kell system and Era antigens. EGA-treated RBCs were tested in parallel with chloroquine diphosphate (CDP)-treated RBCs to evaluate whether EGA would remove Bg antigens from RBCs as efficiently as CDP. Fifty-seven serum/plasma samples containing known Bg antibodies were tested with untreated Bg+ RBCs, EGA-treated Bg+ RBCs, and CDP-treated Bg+ RBCs by an indirect antiglobulin test (IAT), using a low-ionic-strength additive solution and murine monoclonal polyspecific antiglobulin reagent. Of 57 samples, 40 (22 anti-Bga, 17 anti-Bgb, and 1 Bg-related) were nonreactive by IAT with EGA-treated RBCs and CDP-treated RBCs, 14 (7 anti-Bga, 4 anti-Bgb, and 3 Bg-related) were nonreactive by IAT only with EGA-treated RBCs, none were nonreactive in IAT with only CDP-treated RBCs, and 3 (anti-Bga) were still reactive by IAT with EGA-treated RBCs and CDP-treated RBCs. Therefore, EGA strips Bg antigens from RBCs. Our results indicate EGA treatment is more efficient and requires less time (1–2 minutes) to perform than the CDP procedure (30–120 minutes) for removal of Bg antigens from RBCs. Immunohematology 1999;15:66–68.

A combination of the effects of rare genotypes at the XK and KEL blood group loci results in absence of Kell system antigens from the red blood cells

A combination of the effects of rare genotypes at the XK and KEL blood group loci results in absence of Kell system antigens from the red blood cells

Review: conditions causing weak expression of Kell system antigens

Review: conditions causing weak expression of Kell system antigens

A Combination of the Effects of Rare Genotypes at the XK and KEL Blood Group Loci Results in Absence of Kell System Antigens From the Red Blood Cells

The 22 antigens of the Kell blood group system are located on a red blood cell (RBC) membrane glycoprotein that shows sequence homology with a family of metalloendopeptidases. Expression of the Kell system antigens is partially governed by XK, an X-linked gene that encodes the Kx protein; absence of Kx results in reduced Kell antigen expression. Almost total absence of Kell antigens from the RBCs of a German man with no symptoms of neuroacanthocytosis could not be due to the Kell-null phenotype, Ko, because his RBCs had very weak expression of Kx antigen and his three children were Kp(a + b+). Kell antigens were normal on the RBCs of his son but weak on those of his two daughters. An Nla III restriction fragment-length polymorphism within the KEL gene showed the Kpa/Kpa genotype in the propositus. Sequencing of his XK gene showed a single base change within the donor splice consensus sequence of intron 2. A BsaAl restriction fragment-length polymorphism showed the mutation in both of his daughters but not in his son. The extreme depression of the Kell antigens of the propositus must be due to a combination of effects, ie, homozygosity for Kpa and deficiency of Kx protein, each of which is capable of causing some degree of weakening of Kell antigens.

The elucidation of a Kell-related autoantibody using ZZAP-treated red cells

Abstract A 61-year-old, nontransfused, Caucasian male was found to have a positive direct antiglobulin test (DAT) and an autoantibody in his serum prior to total hip replacement. Autoabsorption with the patient’s ZZAP-treated red cells failed to absorb the autoantibody, giving a clue to its possible specificity, which was subsequently found to be Kell-system related. In addition, his red cells were found to have a slightly weakened expression of Kell system antigens. The patient was fit and healthy with normal hematological indices at the time of the operation. One year later, the hematological findings remained the same despite the persistence of the autoantibody and a positive DAT. This suggested that the autoantibody was benign, which was supported by a negative in vitro macrophage assay.

Unusual suppression of Kell system antigens in a healthy blood donor.

Red cells of a Kp(a+) donor, ascertained as a result of screening donor red cell units with anti-Kpa, reacted only very weakly with anti-Kpb and demonstrated weakened expression of various other Kell and para-Kell antigens. Family studies revealed a Kp(a+) sister with similarly weakened expression of Kpb and other Kell and para-Kell antigens. Red cell morphology was normal in both of these individuals. This phenotype is different from any previously reported and is named the Allen phenotype.

Evaluation of monoclonal antibodies reacting with Kell system antigens

Until now there have been few reports on monoclonal antibodies reacting with antigens of the Kell system [2, 3, 4] and because of this only five monoclonal antibodies have been sent for investigation for this first workshop.

Antibodies with specificities related to the Kell blood group system

The 22 antigens of the Kell blood group system are located on a red blood cell (RBC) membrane glycoprotein that shows sequence homology with a family of metalloendopeptidases. Expression of the Kell system antigens is partially governed by XK, an X-linked gene that encodes the Kx protein; absence of Kx results in reduced Kell antigen expression. Almost total absence of Kell antigens from the RBCs of a German man with no symptoms of neuroacanthocytosis could not be due to the Kell-null phenotype, K0, because his RBCs had very weak expression of Kx antigen and his three children were Kp(a + b+). Kell antigens were normal on the RBCs of his son but weak on those of his two daughters. An Nla III restriction fragment-length polymorphism within the KEL gene showed the Kpa/Kpa genotype in the propositus. Sequencing of his XK gene showed a single base change within the donor splice consensus sequence of intron 2. A BsaAl restriction fragment-length polymorphism showed the mutation in both of his daughters but not in his son. The extreme depression of the Kell antigens of the propositus must be due to a combination of effects, ie, homozygosity for Kpa and deficiency of Kx protein, each of which is capable of causing some degree of weakening of Kell antigens.