Experiment 11

May 15, 2018 | Author: Rozvan Lanuza | Category: Body Fluids, Blood, Tissue (Biology), Medical Specialties, Hematology
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Rh typing...



1. Characterize completely completely the the Rh antigens antigens (D,C,E,c,e) (D,C,E,c,e) in terms of their biochemical biochemical nature nature and serologic  property.  property. The final result of gene action in RC groups is the production of a biochemical structure! in the Rh system it is a nonglycosylated protein. This means that there are no carbohydrates attached to the  protein. The gene products of R"D and R"CE are remar#ably similar in that both encode for proteins composed of $1% amino acids that tra&erse the cell membrane 1' times and that their seuence differs  by only $$ base pairs. The gene products of  RHCE, RHCe,  RHce, and RHcE and  RHcE are e&en more similar. C and c differ from one another in four amino acid positions, and one amino acid differentiates E from e. nly nly smal smalll loop loopss of the the Rh prot protei eins ns are are e*po e*pose sed d on the the surfa surface ce of the the RC and and pro& pro&id idee the the conformational reuirements for the serologic differences bet+een the Rh blood types. n comparison +ith - and ell () blood groups, -1 cells possess appro*imately 1./ 0 1/ antigens, +hereas homozygous homozygous ell cells ha&e ///  sites. The greatest number of D antigen sites is on cells of the rare Rh phenotype D22. (D22 cells carry only D antigen and completely lac# Cc and Ee.) "o+e&er, "o+e&er, of the commonly encountered encountered Rh genotypes, genotypes,  R2R'  R2R' cells possess the largest number of D antigen sites. 3ummary4     

Rh antigens are non2glycosylated Rh antigens are transmembrane polypeptides and are an integral part of the RC membrane "ighly immunogenic4 5e*t to - and  D6c6E6C6e 7eighs appro*imately 1821%$ #D 7ell de&eloped in early fetal life

'. 9i&e a listing of the Rh antigens antigens in their different different nomenclatures, nomenclatures, and and their freuency of of occurrence

FREQUENCY D: 85% Caucasians, 92% Blacks, 99% Asians C: 68% Caucasians, 27% Blacks, 93% Asians E: 29% Caucasians, 22% Blacks, 39% Asians c: 80% Caucasians, 96% Blacks, 47% Asians e: 98% Caucasians, 98% Blacks, 96% Asians

Researcher4 :-5;dce DCe>DCe dce>dce DCe>DcE DcE>dce R'R'


Researcher4 C-3, Bary -ntonette :. Reference4 Bodern lood an#ing and Transfusion =ractices by "armening

$. 7hat are the causes of false positi&e and false negati&e reactions in Rh typing by the slide method


mproper and inadeuate +ashing of the red cell suspension may cause pseudoagglutination due to the presence of serum macromolecules in the suspension. This should cause a positi&e control as +ell.  b. The presence of strong autoagglutinins in the patients or donors serum may cause agglutination. =roper +ashing and the control are designed to pre&ent or detect this problem. c. -ntibody coating of the red cell (positi&e D-T) can cause a false positi&e reaction, particularly in the +ea# D test. - D-T +ill detect this occurrence. d. - false negati&e reaction may be seen due to the bloc#ing phenomenon. This occurs most commonly in "DA5 due to anti2D. 3ince the red cells antigen sites are hea&ily coated +ith maternal antibody, they may not react +ith the antiserum. e. Aalse positi&e or negati&e reactions may occur in the Rh test due to many of the technical errors.. f. RCs that react +ith one manufacturerFs anti2D reagent but not +ith another may ha&e a partial D antigen. Researcher4 C-3, Bary -ntonette :. Reference4 cache42u#+p2content>uploads>'/11>/>'112Rh2 Typing.docHIcdJ$IhlJenIctJcln#IglJph 8. 7hat is the clinical! significance or importance of Rh typing Transfusion Reactions • Rh antigens are highly immunogenic. The D antigen is themost immunogenic antigen outside the - system. 7hen anti2D is detected, a careful medical history +ill re&eal RC e*posure through  pregnancy or transfusion of products containing RCs. Circulating antibody appears +ithin 1'/ days of  a primary e*posure and +ithin ' to % days after a secondary e*posure. Rh2mediated hemolytic transfusion reactions, +hethercaused by primary sensitization or  secondary immunization, usually result in e*tra&ascular destruction of immunoglobulin2 coated RCs. The transfusion recipient may ha&e an une*plained fe&er, a mild bilirubin ele&ation, and a decrease in hemoglobin and haptoglobin. The direct antihuman globulin test is usually positi&e, and the antibody screen may or may not demonstrate circulating antibody. 7hen the direct antiglobulin test indicates that the recipientFs RCs are coated +ith g9, elution studies may be helpful in defining the offending antibody specificity. f antibody is detected in either the serum or eluate, subseuent transfusions should lac# the implicated antigen. "emolytic Disease of the 5e+born ("D5) • "D5 is briefly described here because of the historic significanceof the disco&ery of the Rh system in elucidating its cause. -s stated pre&iously, anti2D +as disco&ered in a +oman after deli&ery of a stillborn fetus. The mother reuired transfusion. The fatherFs blood +as transfused, and the mother  subseuently e*perienced a se&ere hemolytic transfusion reaction. :e&ine and 3tetson1 postulated that the antibody causing the transfusion reaction also crossed the placenta and destroyed the RCs of the fetus, causing its death. The offending antibody +as subseuently identified as anti2D."D5 caused by Rh antibodies is often se&ere because the Rh antigens are +ell de&eloped on fetal cells, and Rh antibodies are primarily g9, +hich readily cross the placenta. -fter years of research, a method +as de&eloped to pre&entsusceptible (Rh/ D2negati&e) mothers from forming anti2D, thus pre&enting Rh/(D) "D5. Rh2immune globulin, a purified preparation of g9 anti2D, is gi&en to a D2negati&e +oman during pregnancy and follo+ing deli&ery of a D positi&e fetus. Researcher4 C-3,
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