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Transcript
• Definition • Characteristics of ABO blood group • ABO Antigens • ABO Antibodies • ABO Subtypes • • Individual’s will form immune antibodies to ABO blood group antigens they do not possess. The body produce antibody to Antigen who lake it. Result from interaction between the genes it possesses. • The genetic constitution of an individual or group as determined by the particular set of genes it possesses. The different blood groups are inherited, that is passed on from parents to children. • Blood group antigens are actually sugars attached to the red blood cell. • The type of sugar added determines the blood group. • A and B genes do not directly produce antigens produce an enzyme called transferase attaches a sugar molecule to the chemical structure of the antigen sugar molecule responsible for specificity • O antigen no transerase no antigen produced • A and B antigens on surface of RBC protrude from outermost layer of cell membrane • The ABO genes do not code for the production of ABO antigens, BUT rather produce specific glycosyl transferases • ABO produces a specific glycosyl transferases that add sugars to a basic precursor substance on the RBCs • Each gene codes for the production of a specific Transferase enzymes enable us to convert the basic precursor substance to the particular blood group substance. • the H gene (HH/Hh) encodes for an enzyme, which converts the precursor substance in red cells in to H substance (H antigen). • A and B genes encode specific transferase enzymes which convert H substance in to A and B red cell antigens. • Some H substance remains unconverted. Gene Enzyme H L- fucosyltransferase A 3 N-acetyl- D- galactosyl transferase B 3-D- galactosyl transferase O None H substance. A antigen B antigen • O gene encodes for an inactive enzyme, which results in no conversion of the substance in-group O red cells. • This indicates group O individual contains the greatest concentration of H antigen. • Persons who do not inherit H gene are unable to produce H substance • This rare group is referred to as Oh (Bombay group). • The H antigen is present on the red cells in the following diminishing quantity. – O > A2 > B > A2B > A1 > A1B. • present on the surface of red cells as well as tissue and endothelial cells in the body • found in soluble form in plasma & other body secretions in people known as secretors • inherited in simple Mendelian fashion from an individual’s parents • 3 possible genes that can be inherited: A, B, O • A and B genes produce a detectable product • O gene does not produce a detectable product • Express A antigen on RBC surface – Genotypes AA or AO – Have naturally occurring, clinically significant, predominantly IgM (with a small amount of IgG) antibodies against type B (anti-B) – Subgroups • A1 (80%) • A2 (20%) • Significance: some with A2 have antibodies against the A1 subgroup (antiA1) 16 – Express B Ag on RBC surface – Genotypes BB or BO – Have naturally occurring clinically significant, predominantly IgM (with a small amount of IgG) antibodies against type A cells 17 neither A nor B antigens on their RBC – Genotype OO (“universal donors”) – Have naturally occurring, – clinically significant, very high titer, anti-A, anti-B and anti-A,B antibodies – Group O cells have the most H antigen 18 – Express A and B Ag on RBC surface – Genotypes A1B or A2B – have no ABO antibodies (“universal recipients”) 19 • H Antigen • required to produce either A or B antigens • possible genetic combinations: HH, Hh, or hh • HH or Hh (+) produce H Ag 99.99% of population. • hh does not produce H Ag Bombay phenotype (Oh) • anti-H antibodies rare – found only in individuals with Bombay phenotype • Seen on RBC of ABO-Universal distributed • BOMBAY (Oh)PHENOTYPE:–Patients lack the H gene and therefore cannot make H antigen, A or B antigen on their red cells –Have very strong anti-A, anti-B, and anti-H and can only receive cells from a Bombay donor 22 ABO System Phenotype Antigen Natural antibody Genotype A A only Anti-B AA or AO B B only Anti-A BB or BO AB A and B None AB O None Anti-A, Anti-B OO Example of determining offspring blood types from known or suspected genotypes: Genotype parent #1 (AO) Genotype parent #2 (AB) A O A AA AO B AB BO Phenotypes of possible offspring: A, AB, B Frequencies of ABO Blood Groups: Blood Group O Frequency 45% A 41% B 10% AB 4% 1. A variants (A1, A2) • A1 most common (80%) & most antigenic • A1 and A2 differentiated using antisera specific for A1 Ag (anti-A1 lectin) prepared from seed known as Dolichos biflorus (+) reaction with A1 but not A2 • Anti-A reacts with both A1 & A2 but more strongly with A2 2. weak B phenotypes 2-Null phenotypes: (a) Bombay (Oh) • No A, B or H Ag on red cells & secretions • With anti-A, anti-B & anti-H in their sera (b) para-Bombay • Absent or only trace A,B & H Ag’s detected on normal expression in secretions & body fluids • Natural antibodies antigenic stimulus is environmental exposure occurs from birth • Newborns without ABO antibodies of their own; begin to produce Ab with detectable titer at 6 months of age • Other characteristics of ABO antibodies: 1. IgM 2. Reacts at room temp. after an immediate spin • Refer to the presence or absence of water- soluble ABH antigen substances in body fluids (saliva, semen, urine, sweat, tears, etc). • Secretors possess the water soluble (glycoprotein) form of antigen, which appears in most body fluids. • The production of A, B & H antigens in saliva is controlled by a secretor gene. • The relevant gene is called Se, and its allele which amorphic is se. • Pre-transfusion Testing • Prenatal Testing • Presurgical Testing • Paternity Determination • Transplant Matching • Donor Testing THANK YOU