Cromer-related antigens--blood group determinants on decay-accelerating factor

Three new high-prevalence antigens in the Cromer blood group system

BACKGROUND

The Cromer blood group system consists of nine high-prevalence and three low-prevalence antigens carried on decay-accelerating factor (DAF). This report describes three new Cromer high-prevalence antigens, named ZENA, CROV, and CRAM.

STUDY DESIGN AND METHODS

Sequence analyses were performed on DNA from three probands whose serum samples each contained an alloantibody to a high-prevalence antigen in the Cromer blood group system. Polymerase chain reaction-restriction fragment length polymorphism analysis to detect the mutation encoding the CROV- phenotype was performed on 100 Croatian donors. To map the respective epitopes, DAF deletion mutants were tested by immunoblotting with eluates containing the antibodies.

RESULTS

In each proband, sequence analysis revealed a single-nucleotide substitution in DAF: ZENA, 726T>G mutation, predicted change His242Gln; CROV, 466G>A mutation, predicted change Glu156Lys; and CRAM, 740A>G mutation, predicted change Gln247Arg. By analysis of DAF deletion mutants, the CROV antigenic determinant mapped to the complement control protein (CCP) domain 2, which is encoded by exon 3, whereas ZENA and CRAM mapped to CCP4, which is encoded by exon 6.

CONCLUSION

This study describes three novel high-prevalence antigens in the Cromer blood group system each characterized by a predicted single-amino-acid substitution. The antigens have been assigned the following International Society of Blood Transfusion (ISBT) numbers: ZENA is CROM13, CROV is CROM14, and CRAM is CROM15.

SERF: a new antigen in the Cromer blood group system

The Cromer blood group system consists of eight high incidence and three low incidence antigens carried on decay-accelerating factor (DAF). This report describes the identification and characterization of a new Cromer high incidence antigen, named SERF. Sequence analyses of DNA from a Thai female whose serum contained the alloantibody to a high incidence antigen in the Cromer blood group system (anti-SERF) and from her two children were performed. Reverse transcriptase-polymerase chain reaction (RT-PCR) and sequence analysis on cDNA from the proband and PCR-restriction fragment length polymorphism analysis on DNA from Thais were also performed. To map the epitope, DAF deletion mutants were tested by immunoblotting with anti-SERF. Sequence analysis revealed a substitution of 647C>T in exon 5 DAF in the proband. The proband's two children and two of 100 Thais were heterozygotes 647C/T. Analysis using DAF deletion mutants revealed the antigenic determinant to be within short consensus repeat 3 (SCR3), which is encoded by exon 5. This study describes a novel high incidence antigen (SERF) in the Cromer blood group system characterized by the amino acid proline at position 182 in SCR3 of DAF. The SERF-negative proband has a substitution mutation that predicts for leucine at this position. SERF has been provisionally assigned the International Society of Blood Transfusion number 021.012 (CROM 12).

Decay-Accelerating Factor Deficiency Increases Susceptibility to Dextran Sulfate Sodium-Induced Colitis: Role for Complement in Inflammatory Bowel Disease

Decay-accelerating factor (DAF or CD55) is expressed on colonic epithelial cells but its function in the mucosa is unknown. In humans, a proportion of DAF-deficient (Cromer INAB) patients develop inflammatory bowel disease (IBD). To evaluate how DAF deficiency may contribute to gut inflammation and thus could play a role in IBD pathogenesis, we compared the severity of dextran sulfate sodium-induced colitis in Daf1 gene-targeted and control mice. Seven days after consuming 3% dextran sulfate sodium in their drinking water, Daf1(-/-) mice suffered markedly greater weight loss (-24.7 +/- 7.5% vs -14.2% +/- 4.9%), exhibited uniformly bloody diarrhea as compared with soft stool in control mice, developed shortened colons, and had larger spleens. Histological examination of distal colons showed massively increased neutrophilic and mononuclear cell infiltration, greater epithelial cell destruction, and increased ulcerations. Cytokine production in organ cultures of colonic explants showed increased levels of IL-12 and IL-6. Fourteen days after switching back to regular water, in contrast to the Daf1(+/+) controls which showed little stool abnormality, all Daf1(-/-) mice continued to have diarrhea. Organ culture cytokine measurements at this time point, i.e., the end of the recovery phase, showed markedly increased levels of IL-10 (6-fold), IL-12 (4-fold), and IL-6 (2-fold), as well as TNF-alpha (>10-fold) compared with the controls. Our findings argue that, as shown for IL-10 in IL-10(-/-) mice and IL-2 in IL-2(-/-) mice, DAF control of complement additionally is important in regulating gut homeostasis and consequently its activity may participate in protecting against IBD.

GUTI: a new antigen in the Cromer blood group system

BACKGROUND

The Cromer blood group system consists of seven high-incidence and three low-incidence antigens carried on decay-accelerating factor (DAF). This report describes the identification and characterization of a new Cromer high-incidence antigen, named GUTI.

STUDY DESIGN AND METHODS

RT-PCR and sequence analysis were performed on cDNA prepared from a Chilean donor whose serum contained the alloantibody (anti-GUTI). Based on the observed point mutation, a PCR-RFLP assay using MaeII was developed. To map the epitope, DAF-deletion mutants were tested by immunoblotting with anti-GUTI.

RESULTS

Sequence analysis revealed a substitution of 719G>A in DAF in the proband. The proband's parents and two daughters were heterozygotes for 719G>A, one sister whose RBCs typed GUTI- was homozygous for 719A, and one sister had the wild-type DAF (719G). Seven additional heterozygote samples were identified among 214 Chileans. No heterozygotes were found in 197 New York donors. Analysis using DAF-deletion mutants showed the antigenic determinant to be within short consensus repeat (SCR) 4.

CONCLUSION

This study describes a novel high- incidence antigen (GUTI) in the Cromer blood group system characterized by the amino acid arginine at position 206 in SCR4 of DAF. The GUTI-negative proband has a substitution mutation that predicts for histidine at this position.

Severe autoimmune hemolytic anemia caused by a warm IgA autoantibody directed against the third loop of band 3 (RBC anion-exchange protein 1)

BACKGROUND

Autoimmune hemolytic anemia associated with only IgA autoantibodies reacting optimally at 37 degrees C (WAIHA) is exceedingly rare. When identified, warm IgA autoantibodies specificities are usually directed to antigens of the Rh system. However, like IgG autoantibodies, the specificity of the majority of these antibodies is not identified.

CASE REPORT

A case of a 3-year-old boy in whom a life-threatening IgA WAIHA occurred suddenly is reported. Following initial RBC transfusions and treatment with steroids at a dose of 3 mg per kg, which was slowly tapered, stabilization to a state of compensated hemolysis was achieved, persisting 4 months before complete resolution. There was no recurrence within a 16-month follow-up.

STUDY DESIGN AND METHODS

The standard DAT in a gel column method with anti-IgG and anticomplement reagents was negative. However, the same method with an anti-IgA was strongly positive.

RESULTS

The serum and the eluate obtained after acid elution reacted with all normal RBCs tested. Enzymatic treatment of panel RBCs by alpha-chymotrypsin and pronase abolished the reactivity. The reaction was completely inhibited by RBC incubation with four different MoAbs directed against the third extracellular loop of band 3, the RBC anion-exchange protein 1 (AE1), whereas MoAbs against other specificities showed no effect.

CONCLUSIONS

This is the first report of an IgA autoantibody directed against the band 3 (AE1) protein and, more specifically, against the third loop. Moreover, this case underlines the importance of including IgA research in the initial diagnostic evaluation when a hemolytic anemia is suspected to be autoimmune and when IgG and complement are not detected on the patient's RBCs.

Molecular basis of Cromer blood group antigens

BACKGROUND

The Cromer blood group system consists of 10 antigens located on decay-accelerating factor (DAF). Previous molecular genetic analysis has determined the basis for four of these antigens. The present study was undertaken to identify the mutations that determine the remaining antigens.

STUDY DESIGN AND METHOD

Existing or new data were used to localize each Cromer system antigen to a specific short consensus repeat (SCR) domain of DAF. The exon encoding that SCR domain was amplified by using the polymerase chain reaction (PCR) on genomic DNA obtained from individuals of that Cromer phenotype, and the DNA product was subjected to DNA sequence analysis.

RESULTS

The Tc(a)/Tc(c) polymorphism is due to an R18P amino acid substitution in SCR1 of DAF. The Es(a+)/Es(a-) polymorphism is due to an I46N mutation in SCR1 of DAF. The WES(b)/WES(a) polymorphism is due to an L48R mutation in SCR1 of DAF. The UMC+/UMC- polymorphism is due to a T216M substitution in SCR4 of DAF.

CONCLUSIONS

With information from previous reports and the findings of this study, the molecular genetic basis of all known alleles of the Cromer blood group system has been elucidated. Single amino acid substitutions are responsible for 9 of the 10 antigens (all except the multiple-epitope antigen IFC).

Disappearance of antibodies to Cromer blood group system antigens during mid pregnancy

The Cromer blood group system consists of 7 high incidence and 3 low incidence antigens that are carried on the complement regulatory glycoprotein called decay-accelerating factor (DAF; CD55). Despite laboratory results that would predict clinical significance, antibodies with specificities in the Cromer blood group system have not been reported to cause hemolytic disease of the newborn. It is possible that strong expression of DAF on the apical surface of antigen-positive fetally derived placental trophoblasts may absorb maternal antibodies that are directed to antigens in the Cromer blood group system. We studied two cases where strongly reactive anti-Cra and anti-Dra became undetectable during second and third trimesters of pregnancies.

What is important on the red blood cell surface

Blood group antigens have provided tools for investigation of the red cell surface and been very useful as genetic markers in family, population and forensic studies. Precise definition of phenotypes is very important. Application of MAIEA (monoclonal antibody-specific immobilisation of erythrocyte antigen), a recently reported technique, to identify antigens and to assign red cell antigens to a particular membrane component is described: location of Knops system antigens on CR1 is confirmed and provisional assignment of Cromer system antigens to the different short consensus regions of decay accelerating factor (DAF) is described. Variability of red cell antigen expression is considered. The possibility is discussed that factors other than alterations in Rh genes may be responsible for some Rh variant phenotypes. Some C variants, two of which are associated with low incidence antigens, are described. The relationship of Xga with the quantitative polymorphism of 12E7 antigen is reconsidered in light of some recent immunochemical studies.

Nonlethal adherence to human neutrophils mediated by Dr antigen-specific adhesins of Escherichia coli

Uropathogenic Escherichia coli strains express a variety of adhesins, including members of the Dr adhesin family such as the Dr hemagglutinin, AFAI, and AFAIII. Certain E. coli adhesins (e.g., type 1 and S fimbriae) are known to mediate adherence to human polymorphonuclear leukocytes (PMNs). The receptor on erythrocytes for Dr family adhesins, decay accelerating factor, is also present on PMNs. To determine whether Dr family adhesins mediate adherence to PMNs and to characterize the specificity and consequences of such adherence, we studied agglutination of PMNs and adherence to PMNs by recombinant E. coli strains expressing various mannose-resistant or mannose-sensitive adhesins, in the presence or absence of inhibitors of adherence. Dr family adhesins, like type 1 fimbriae, mediated concentration-dependent adherence to PMNs. Adherence to PMNs was mannose sensitive for type 1 fimbriae but mannose resistant for Dr family adhesins. Chloramphenicol inhibited PMN adherence for the Dr hemagglutinin with the same potency as that with which it inhibited hemagglutination, but it was inactive against PMN adherence and hemagglutination mediated by other members of the Dr adhesin family. In contrast to PMN adherence mediated by type 1 fimbriae, adherence mediated by the Dr hemagglutinin did not lead to significantly increased bacterial killing. These data suggest that Dr family adhesins mediate a novel pattern of adherence to PMNs, probably by recognizing decay accelerating factor, with minimal consequent bacterial killing.

Use of the MAIEA technique to confirm the relationship between the Cromer antigens and decay-accelerating factor and to assign provisionally antigens to the short-consensus repeats

The MAIEA (monoclonal-antibody-specific immobilisation of erythrocyte antigens) assay has recently been developed for the assignment of red cell antigens, recognised by human alloantisera, to particular membrane components of the red cell membrane. This technique detects trimolecular complexes formed by the reaction of a human antibody and a mouse antibody with a particular red cell protein. A positive reaction, in an ELISA-type detection procedure, occurs if the epitopes to the human and mouse antibodies are present on the same membrane component but at different regions. In this report, we show how the MAIEA assay can be used to confirm the relationship between Cromer system antigens and the complement-regulatory protein, decay-accelerating factor (DAF, CD 55). In addition, the location of the antigens along the protein is postulated by using three anti-DAF monoclonal antibodies with specificities to different regions of DAF. Tca and Esa are assigned provisionally to the first short-consensus repeat (SCR), UMC to the second SCR, Dra to the third SCR and Cra, WESa and WESb to the fourth SCR or to the serine/threonine rich region of the DAF protein.

[Rapid diagnosis of paroxysmal nocturnal hemoglobinuria by gel test agglutination]

Murine monoclonal antibodies (MoAbs) directed against DAF (Decay Accelerating Factor, CD55 antigen) and MIRL (Membrane Inhibitor of Reactive Lysis, CD59 antigen) were used to identify the affected red cells (CD55-/CD59-) of PNH patients. MoAbs NaM16-4D3 (CD55, IgG2a) and NaM77-1E5 (CD59, IgG3) weakly agglutinate red cells and represent powerful tools to quantitate normal (PNHI) and abnormal (PNHII and PNHIII) cells from PNH patients by indirect flow cytometry. MoAbs NaM125-7H10 (CD55) and NaM123-6G12 (CD59), both IgM, were selected for their agglutinating properties and used for the separation of PNHI from PNHII and PNHIII red cells by the gel test technology. From analysis of artificial mixtures of DAF+ and DAF- cells, a direct relationship was established between fluorescent cells detected by flow cytometry, and erythrocytes agglutinated in microtyping cards. The method was further confirmed by analysis of ten blood samples from PHN patients and represent an alternative to classical hemolysis tests. On the basis of our experience we propose the following for the diagnosis of PNH: 1) agglutination test with NaCl microtyping cards using IgM CD55 and CD59; 2) flow cytometry analysis for accurate quantitation of CD55-/CD59- red cells.

Complement and pregnancy: new insights into the immunobiology of the fetomaternal relationship

Recent studies have revealed that human trophoblast expresses three membrane-bound proteins which function specifically to regulate the activity of complement. These proteins are already known to be widely distributed in normal adult tissues where they protect host cells from damage resulting from the fortuitous deposition of activated complement components. Their activities are focused at two distinct steps in the complement pathway. Decay accelerating factor (DAF, CD55) and membrane co-factor protein (MCP, CD46) act at the level of the C3 convertase enzymes which activate C3 to C3b. A further protein, CD59, directly regulates the formation and function of the terminal cytolytic membrane attack complex (MAC) by specifically interacting with C8 and C9. These proteins appear to play an important role in the maintenance of normal human pregnancy. DAF, MCP and CD59 are all expressed where trophoblast surfaces are in contact with maternal blood and tissues and expression occurs from at least 6 weeks of gestation. The semi-allogeneic human conceptus therefore appears to be effectively protected from maternal complement-mediated damage arising either from alternative or classical pathway activation or in a bystander fashion following a response to microbial infection in the mother. Complement regulatory protein deficiency disorders with clinically demonstrable consequences especially in terms of haemolytic disease are known to exist and have proved valuable in establishing the biological role of these proteins in vivo. The demonstration of this new family of immunoregulatory proteins on trophoblast raises important questions about the potential involvement of these products in pregnancy pathologies.

Complement

The complement system mediates a wide range of important biological functions. The use of modern techniques in protein chemistry and molecular biology has greatly facilitated our understanding of the interactions between the fluid phase and cell-bound components of the system. Structural and genetic analysis has shown that while many of these components are polymorphic, there are major similarities between many of the proteins serving enzymatic and regulatory roles in both the alternative and classical pathways. The regulation of complement activation and Class III genes, on chromosomes 1 and 6 respectively, encode nine of the major proteins in the system. The genetic basis of C4 and C3 polymorphisms is now well established, and further study may reveal functional differences between polymorphic variants of other components. The study of individuals with either genetic or acquired deficiencies of complement proteins and receptors has provided insight into the function of these components, leukocyte adherence deficiency (LAD) providing the best example. An appreciation of the genetics, structure and functions of the regulatory proteins decay-accelerating factor (DAF) and homologous restriction factor has enhanced our understanding of the pathogenesis of paroxysmal nocturnal haemoglobinuria. The full importance of CD59 glycoprotein, the newest member of the complement family, remains to be determined.

Phosphatidylinositol-glycan linked proteins of the erythrocyte membrane

The human erythrocyte bears a number of proteins anchored to the outer membrane surface via a phosphatidylinositol-glycan linkage. This class of proteins includes several complement regulatory proteins (including decay-accelerating factor, CD59 antigen (protectin), and C8 binding protein) as well as several enzymes and at least one protein important in cell-cell interaction. In addition, a number of blood group antigens have been identified to reside on proteins with phosphatidylinositol anchors. One blood group (Cromer) resides on DAF. Study of variants in this blood group system has led to interesting information about the function and expression of this protein. Several other blood groups, such as JMH and Holley/Gregory, appear to reside on as yet unidentified phosphatidylinositol-linked proteins. In paroxysmal nocturnal haemoglobinuria, a variable proportion of red cells fail to express or express weakly all phosphatidylinositol-linked proteins. The origin of this deficiency is now being worked out. In addition, individuals with inherited deficiency of DAF or CD59 (protectin) have been identified. Only the latter deficiency leads to a PNH-like syndrome.

Dr(a-) polymorphism of decay accelerating factor. Biochemical, functional, and molecular characterization and production of allele-specific transfectants

The Dra antigen belongs to the Cromer-related blood group system, a series of antigens on decay accelerating factor (DAF), a glycosyl-phosphatidylinositol-anchored membrane protein that protects host cells from complement-mediated damage. We studied the rare inherited Dr(a-) phenotype to ascertain the associated biochemical and functional changes in DAF and to characterize the basis for this polymorphism. Radioimmunoassay assay and flow cytometric analysis of Dr(a-) erythrocytes demonstrated 40% of normal surface expression of DAF but normal levels of several other glycosyl-phosphatidylinositol-anchored proteins, distinguishing this phenotype from that of paroxysmal nocturnal hemoglobinuria. Western blots confirmed this reduced DAF expression and indicated a slightly faster mobility of the molecule on SDS-PAGE. Despite the reduced DAF expression, Dr(a-) erythrocytes functioned normally in the complement lysis sensitivity assay. Utilization of the polymerase chain reaction to amplify mononuclear cell genomic DNA from three unrelated Dr(a-) individuals demonstrated that a point mutation underlies the Dr(a-) phenotype: a C to T change in nucleotide 649 resulting in a serine165 to leucine change. This defines the Drb allele of DAF, which can be distinguished from Dra by a Taq I restriction fragment length polymorphism. We created transfected Chinese hamster ovary cell lines expressing either the Dra or the Drb allelic form of DAF. These allele-specific transfectants were tested by inhibition of hemagglutination or flow cytometry and confirmed the specificity of anti-Dra alloantisera. The allele-specific transfectants could form the basis of a new serological approach to immunohematology.

The Dr hemagglutinin, afimbrial adhesins AFA-I and AFA-III, and F1845 fimbriae of uropathogenic and diarrhea-associated Escherichia coli belong to a family of hemagglutinins with Dr receptor recognition

The receptor specificities of four Escherichia coli cloned hemagglutinins, AFA-I, AFA-III, F1845 fimbriae, and the Dr hemagglutinin were studied. Evidence is provided that all four hemagglutinins recognize as their receptor the Dr blood group antigen. However, results of experiments using enzyme-treated erythrocytes and monoclonal antibodies indicate that the four adhesins recognize different epitopes on the Dr antigen and thus constitute a family of Dr receptor-recognizing bacterial adhesins. Furthermore, the same results suggest that the Dr antigen itself may be divided into subcomponents on the basis of bacterial adhesins.