Biomedical subjects

Christine Lomas-Francis

Publications and source records attributed to Christine Lomas-Francis.

6 recordsLinked to original sources

PubMed2006

Molecular basis of two novel high-prevalence antigens in the Kell blood group system, KALT and KTIM.

BACKGROUND: The Kell blood group system consists of 25 antigens that result from single-nucleotide polymorphisms. Most polymorphic Kell antigens reside on the N-terminal domain of Kell before the zinc-binding catalytic motif, which is the major site for endothelin-3-converting enzyme activity. Kell antigens are important in transfusion medicine owing to their strong immunogenicity, and the corresponding antibodies are clinically significant. Two probands were studied whose serum samples contained antibodies to different high-prevalence Kell antigens. STUDY DESIGN AND METHODS: Standard hemagglutination methods were used for serologic testing of Proband 1 and Proband 2. DNA was prepared from both probands and family members. The 19 exons and the intron-exon regions of KEL from both probands were amplified by polymerase chain reaction, and the sequences were compared with that of common KEL. The identified substitutions were located on a three-dimensional model of Kell generated based on the crystal structure of neutral endopeptidase, a homolog of Kell. RESULTS: In Proband 1, a homozygous 1988G>A mutation (Arg623Lys) in Exon 17 was present. One sibling of Proband 1 was homozygous for 1988G>A. In Proband 2, a homozygous 1033G>A mutation (Asp305Asn) in Exon 8 was present. Three siblings of Proband 2 were heterozygous for 1033G>A. CONCLUSION: The identified KEL mutations of the two probands are novel and inherited. The antigen absent from the red blood cells (RBCs) of Probands 1 and 2 are named KALT and KTIM, respectively. KALT is unique in that it is the only Kell antigen sensitive to treatment of RBCs by trypsin.

Amino Acid Substitution↗

PubMed2006

Case report and literature review: transient Inab phenotype and an agglutinating anti-IFC in a patient with a gastrointestinal problem.

BACKGROUND: The Inab phenotype is a rare deficiency of all Cromer antigens. These antigens are carried on the decay-accelerating factor (DAF, CD55) molecule that is attached to the red blood cell (RBC) membrane by a glycosylphosphatidylinositol (GPI) anchor. Although typically inherited, an acquired and transient form of the Inab phenotype also exists. A patient with the triad of transient Inab phenotype, a direct-agglutinating anti-IFC, and gastrointestinal (GI) abnormalities is reported. CASE REPORT: An 18-month-old boy with gastroesophageal reflux disease requiring a feeding tube, milk and soy intolerance, and severe growth retardation, as well as vision and hearing deficits from cytomegalovirus infection, was identified when pretransfusion testing revealed a potent panagglutinin (titer > 2000 at 4 degrees C). This antibody did not react with Dr(a-) and IFC RBCs, and the autocontrol was negative. The patient's RBCs lacked CD55 by flow cytometric techniques but had normal levels of CD59 and antigens such as Yt(a) and Emm, carried on GPI-linked proteins, thus excluding paroxysmal nocturnal hemoglobinuria. Several months after initial detection, the anti-IFC was virtually undetectable and his cells reacted weakly with anti-IFC, anti-Dr(a), and anti-CD55. RBCs from the propositus' parents and brother demonstrated normal CD55 and CD59 expression. CONCLUSION: This is the first example of a direct-agglutinating anti-IFC. The cause of the transient depression in CD55 protein (and thus Cromer system antigens) and appearance of anti-IFC remains unknown, as does the relationship between the patient's GI system abnormalities and these serologic findings.

Agglutination↗

PubMed2005

A flexible array format for large-scale, rapid blood group DNA typing.

BACKGROUND: Typing for blood group antigens is currently performed by hemagglutination. The necessary reagents are becoming costly and limited in availability, and the methods are labor-intensive. The purpose of this study was to determine the feasibility of the use of large-scale DNA analysis in a microarray as a substitute for blood group typing. STUDY DESIGN AND METHODS: DNA, extracted from blood samples that had been phenotyped for some of the red blood cell antigens, was analyzed for selected blood group alleles by bead array (BeadChip, (BioArray Solutions Ltd., Warren, NJ) Illumina) [corrected] and by manual polymerase chain reaction (PCR)-based assays. Selected alleles were identified by enzyme-mediated elongation of probes, which were on color-encoded beads assembled into arrays on silicon chips. The performance of a prototype BeadChip (BioArray Solutions Ltd., Warren, NJ) [corrected] (BLOOD-1) containing single-nucleotide polymorphisms (SNPs) for FYA/B, FY-GATA, DOA/B, COA/B, LWA/B, DIA/B, and SC1/SC2 was verified with DNA from serologically characterized donors. It was then used to analyze more than 400 samples of partially defined phenotype. Samples from Chinese, Ashkenazi, and Thai donors (total n = 227) were tested with BLOOD-1. An expanded BeadChip (BioArray Solutions Ltd., Warren, NJ) [corrected] with a total of 18 SNPs (36 alleles; SNPs in BLOOD-1 and M/N, S/s, Lu(a)/Lu(b), K/k, FY265[for the Fy(X) polymorphism], Jk(a)/Jk(b), DO323[for Hy], DO350[for Jo(a)], and HgbS) was then evaluated with a subset of previously tested samples from Chinese, Ashkenazi, and New York blood donors (127) and an additional set of samples from Israeli donors (total n = 188). RESULTS: Results obtained by BeadChip (BioArray Solutions Ltd., Warren, NJ) [corrected] analysis were concordant with those obtained with the manual PCR-restriction fragment length polymorphism, allele-specific PCR, and hemagglutination assays. The frequencies of the alleles in the samples from different ethnic panels were within the expected ranges; however, two new DO alleles were discovered. CONCLUSION: It has been shown that microarray technology can be used to type DNA and detect new alleles in donor cohorts.

Alleles↗

PubMed2004

A new hybrid RHCE gene (CeNR) is responsible for expression of a novel antigen.

BACKGROUND: The red blood cells (RBCs) of a patient, known to have the probable DC(W)(e)/D-- phenotype, typed as D(W)- and Rh32- but were unexpectedly agglutinated by an anti-D(W)/Rh32 serum. The reactivity suggested that the RBCs carried a novel antigen and that the molecular background of this DC(W)(e)/D-- phenotype might be different from those reported. The purpose of this study was to determine the molecular basis of the Rh phenotype. STUDY DESIGN AND METHODS: Samples were obtained for family studies. Standard hemagglutination methods were used. RH mRNA transcripts were isolated by reverse transcription-polymerase chain reaction and sequenced. RESULTS: Sequence analysis revealed that the probond had three different RH transcripts: a normal RHD and two different hybrid transcripts from the RHCE locus, a RHCE-D hybrid with exon 1 from RHCE associated with the D-- haplotype, and a new RHCE-D hybrid. In this new hybrid, exons 1 to 5 are RHCe-specific and exons 6 to 10 correspond to RHD. The C(W) antigen is also encoded by this hybrid gene. Family studies confirmed that the new RHCE-D hybrid is linked in cis to conventional RHD. CONCLUSION: A new RHCE-D structure is associated with altered expression of C and e antigens in this family and the generation of a novel low-prevalence antigen (CENR).

Amino Acid Sequence↗

PubMed2003

DAK, a new low-incidence antigen in the Rh blood group system.

BACKGROUND: Some low-incidence antigens in the Rh blood group system (e.g., VS, Rh32, FPTT) are expressed by more than one Rh complex. We describe a new low-incidence antigen that is present on RBCs with the partial D phenotypes, DIIIa or DOL, on RN RBCs and on one example of STEM+S RBCs. STUDY DESIGN AND METHODS: Standard hemagglutination testing was performed with two sera that agglutinated DIIIa RBCs on our in-house antibody identification panel. DNA-based assays were performed on selected samples. RESULTS: RBCs with the DIIIa (n = 31), DOL (n = 5), or RN (n = 10) phenotype were agglutinated by both sera, as were RBCs from one STEM+S person. Reactivity with RBCs of either DIIIa or DOL phenotypes was stronger than with RN RBCs and could not be separated by adsorption and elution. CONCLUSION: An antibody, anti-DAK, which recognizes a novel low-incidence antigen that is more strongly expressed on DIIIa and DOL RBCs than on RN RBCs is described. The antibody agglutinated RBCs from 4 percent of D+ African American blood donors in New York. The antigen, DAK, has been assigned the ISBT number RH54 (004.054).

Adolescent↗

PubMed2002

Molecular approaches to blood group identification.

Allogeneic barriers to transfusion are caused by differences between those portions of the donor and recipient genomes that define the antigenicity and immune response to the transfused cells. Historically, a blood group antigen was identified when an immune response (alloantibody) was detected by hemagglutination in the serum of a transfused patient. There has been an astounding pace of growth over the past two decades in the field of molecular biology techniques and even more recently in the understanding of the basis of many blood group antigens and phenotypes. Identification of blood group antigens can now be performed in genetic terms, and identification of blood group antibodies can be performed using molecular approaches. This knowledge is being applied to help resolve some long-standing clinical problems that cannot be resolved by classical hemagglutination. This article reviews knowledge of molecular approaches for identifying blood group antigens and antibodies as applied to transfusion medicine practice.

Animals↗