Harvard-MIT Division of Health Sciences and Technology HST.071: Human Reproductive Biology Course Director: Professor Henry Klapholz IN SUMMARY ISO-IMMUNIZATION ISOIMMUNIZATION History Of Rh Isoimmunization •The Rh story is one of multiple foci of independent investigations –Occurring at different sites –Different times •High level of competition that can develop –Laboratory scientists –Clinical scientists –Pharmaceutical industry Ortho Pharmaceutical Company • Trade name RhoGAM, three decades ago • Rh Isoimmunization affected approximately 1 percent of the pregnancies in the U.S. at the beginning of this century Clinical findings • Hemolytic anemia • Edema of the fetal tissues known as hydrops (eryhtroblastosis) fetalis • Autopsy evidence of proliferation of red blood cells in multiple sites • Large of number of immature red cells • 1930s -recognized as one clinical entity were • Hydrops fetalis • Icterus gravis neonatorum • Congenital anemia • Erythroblastosis fetalis • World War II lead to discovery of antigenic blood factors, which might result in immunization and cause transfusion reactions. • Major contributors • Alexander Wiener • Philip Levine, • Karl Landsteiner Causes of fetal hydrops  Lymphatic Abnormalities • Lymphangiectasia • Cystic hygroma • Turner's syndrome (XO) • Noonan's syndrome • Multiple ptergium syndrome • Pulmonary Malformations • Lymphangiectasia • Chylothorax • Cystic adenomatoid malformation • Hypoplasia • OtherIN SUMMARY ISO-IMMUNIZATION  Hematologic • Fetal hemolytic anemia • α-Thalassemia • Fetomaternal or twin-to-twin transfusion  Congenital Infections • Viruses • Cytomegalovirus • Parvovirus B19 • Toxoplasmosis • Syphilis • Chagas Disease  Cardiovascular • Arrhythmias • Cardiomyopathy • Structural anomalies: lesions that result in increased right atrial pressure and volume • primarily with atrioventricular regurgitation • left sided obstructive lesions • Ebstein's anomaly • Premature closure of the foramen ovale • Intracardiac tumors (tuberous sclerosis) • Vascular malformations • Chorangioma of the placenta, chorionic or umbilical vessels • Hemangiomas (Hepatic, Klippel-Trenaunaysyndrome)  Other Causes • Obstructive uropathy • Congenital nephrosis • Chromosomal abnormalities • Trisomy 15, 18, 21 • XX/XY • Neoplasms • Storage diseases • Bone diseases • Placental abnormalities • Neurologic abnormalities • Idiopathic Genetics and Biochemistry of the Rh Antigen Nomenclature •1940, Landsteiner and Wiener -rabbit immune sera to rhesus monkey erythrocytes •Agglutinated the majority (85 percent) of human erythrocytes •Named this the Rh factor. •Agglutinated cells were called Rh positive •Disease caused by antibody directed against an erythrocyte surface antigen of the rhesus blood group system. •High degree of polymorphism Five major antigens can be identified • Many variant antigens • Three Systems of Categorization • Fisher-Race • Wiener system • HLA-like system of RosenfieldIN SUMMARY ISO-IMMUNIZATION Fisher-Race System • Nomenclature is best known in Obstetrics • Presence of three genetic loci • Each with two major alleles • C, c, D, E, and e • No antiserum specific for a "d" antigen • "d" indicates the absence of a discernible allelic product • Anti-C, anti-c, anti-D, anti-E, and anti-e designate specific anti-sera directed against the respective antigens. • Rh gene complex described by the three appropriate letters Rh Antigen Complexes Eight gene complexes (decreasing frequency in humans) Cde cde Cde cDe Cde cdE CDE CdE Table removed due to copyright restrictions. [Rh Gene Frequencies in 2000 Unrelated Caucasian Adults] Nomenclature • Written in the order C(c), D(d), E(e) • Actual order of the genes on chromosome 1 is D, C(c), E(e). • Vast majority of Rh Isoimmunization -incompatibility with respect to the D antigen • Rh positive indicates the presence of the D antigen • Rh negative indicates the absence of D antigen Weiner System • Assumption of only one genetic locus • Eight genotypes are designated (in decreasing order of frequency in the white population) R1, r, R2 , R0r, r, RZ , and rv.IN SUMMARY ISO-IMMUNIZATION Variants of D Antigen • Unique Rh antibodies have been used to identify more than 30 antigenic variants • Two of the most common • CW antigen • Du antigen • Heterogeneous group of clinically important D antigen variants most often found in African Americans • Du -positive individuals -quantitative decrease in expression of the normal D antigen, • Some Du variants are significantly different antigenically • Two cellular expressions responsible for the Du phenotype • Reduction in the number of D antigen sites with all epitopes represented • Expression of only some of the various D antigen epitopes with some epitopes missing Du Variant • Du -positive erythrocytes -bind anti-D typing sera • In some cases only by sensitive indirect antiglobulin methods • At least some Du -positive patients are capable of producing anti-D, presumably by sensitization to missing D epitopes. • Could result in a Du -positive mother becoming sensitized to her D-positive fetus Genetic Expression • Genetic locus for the Rh antigen on the short arm of chromosome 1 • Within the Rh locus are two distinct structural genes adjacent to one another, • RhCcEe and RhD. • Likely share a single genetic ancestor, • Identical in more than 95 percent of their coding sequences • First gene codes for the C/c and E/e antigens • Second gene codes for the D antigen • D-negative lack the RhD gene on both their chromosomes. • D-negative patients have a deletion of the D gene on both their chromosomes 1 • Expression of the Rh antigen on the erythrocyte membrane o Genetically controlled o Structure of the antigen o Number of specific Rh-antigen sites (e.g., D, E, C, c, or e) o Relatively constant amount of Rh antigen sites available o About 100,000 sites per cell o Evenly divided between C(c), D, and E(e) antigens Allelic Interactions • CDe/cde express less D antigen than cDE/cde. • CDe/cDE express less C antigen than CDe/cde Structure and location of antigens • The Rh antigens -polypeptides • Embedded in the lipid phase of the erythrocyte membrane • Distributed throughout the