ABO Subgroups - Immunohematology Past Paper PDF

IMMUNOHEMATOLOGY / ISBB / IH LESSON#4: ABO SUBGROUPS PRELIMS | A.Y. 2023 - 2024 | SIR JASON “AB” CHUA ABO SUBGROUPS A2 individuals only have A antigen present o...

IMMUNOHEMATOLOGY / ISBB / IH LESSON#4: ABO SUBGROUPS PRELIMS | A.Y. 2023 - 2024 | SIR JASON “AB” CHUA ABO SUBGROUPS A2 individuals only have A antigen present on the red cell. ABO phenotypes can be divided into categories also known as ○ The absence of A1 antigen will prevent its ability to subgroups recognize A1 antigens. ○ The antigens differ in the amount expressed on the ○ Has the capability of producing anti-A1(only few) red cell membrane A2B individuals are able to receive A gene and B gene from one ○ Also differs in the quality of the antigen parent. However, the A gene inherited is A2. Meaning, linear A Some are linear, some are branched. antigen will be present. ○ It cannot recognize A1 antigens, the same with A2 A SUBGROUPS phenotype. Question: What would eventually happen if an A2 individual will QUANTITATIVE AND QUALITATIVE DIFFERENCES be transfused with A1 red cells in w/c it can’t recognize the A1 Initiated by Von Dungern, 1911 antigens? Described 2 antigens of the A phenotype based on the ○ Anti-A1 antibody is naturally occuring. However, the reactions on group A RBCs with the antibodies, anti-A and majority of it is in the form of IgM. anti-A1. ○ The Anti-A1 antibody is also clinically insignificant The A phenotype has two subgroups: A1 and A2 because unlike other ABO antibodies that are able to ○ Quantitative differentiation is based on the number activate the complement at body temperature of antigens regardless if it is IgG or IgM. The anti-A1, despite ○ Qualitative differentiation is based on the structure being classified as IgM, is not reactive at body of the antigen temperature. QUANTITATIVE A1 A2 ○ Thus, A2 individuals can receive red cells containing A1 antigen.The same goes for A2 No. of Antigen Sites More (810k-1.17M) Less (240k-290k) ○ Although anti-A1 is clinically insignificant, it causes Amt. of transferase enzyme discrepancies during blood typing, specifically the (alpha-3-n-acetyl-d- More Less forward and reverse typing. galactosamine transferases) Will cause differences in the result of both Amt. of branching of precursor More (Branched) Less (Linear) tests. substances The number of antigen sites in the RBC surface is d/t by the NOTE: HARMENING Anti-A1 is a naturally occurring IgM cold-reacting antibody and amount of transferase enzymes. is unlikely to cause a transfusion reaction b/c it usually reacts ○ Gene A1 is much more capable of producing more only at temperatures well below 37°C. transferase enzyme It is considered clinically significant if it is reactive at 37°C. The enzyme for A1 and A2 is ○ This antibody can cause discrepancies between alpha-3-n-acetyl-d-galactosamine transferases. forward and reverse ABO testing and ○ However, the amount of enzyme produced depends incompatibilities in crossmatches with A1 or A1B on the gene. This in turn, attributes to the amount of cells. A antigen present on the RBC membrane. More enzymes = more H antigens placed with n-acetylgalactosamine sugar w/c will FORMATION OF A and A1 antigen later on be converted to A1/A2 antigen Types of H antigen present on RBC Membrane: In A subgroup, antigen is either in branched form or linear. H1 and H2 (only A antigen is present) The A1 individuals, both linear and branched A antigens are ○ Also called as linear H antigen present on the red cell. H3 and H4 (both A1 and A antigen are present) ○ This also explains why it has numerous antigens. ○ Also called as branched antigen In comparison to A2, the number of antigen sites is lesser A1 and A2 genes compared to A2 because of the lesser production of ○ both code for the enzyme transferase enzymes by the A2 gene. α-3-N-acetylgalactosaminyltransferase Recall: it has the same enzyme with A1. Transfers N-acetylgalactosamine sugar of and converts both the branched and linear ○ A2 antigens are mostly linear, contributing to the H antigen reason why there are less antigens. QUALITATIVE A1 A2 A2B A1 GENE Only A antigen is Only A antigen is codes for higher amounts and much more efficient production Diff. In antigen A and A1 of transferase enzymes present present structure antigens (cannot recognize A1 (cannot recognize A1 ○ Converts both linear and branched H antigen (H1 to (antigenic sites) present antigens) antigens) H4) to become A(linear) and A1 antigen(branched) Formation of ○ It is able to transform linear and branched antigen None 1-8% 22-35% Anti-A into A1 antigen A1 individuals, A and A1 antigen are present on the red cell. Thus, in A1 individuals, they have two types ○ Because A1 is both linear and branched and has the of A antigens present on red cell A1 antigen, it can’t form the anti-A1 antibody. membrane – A (linear) and A1(branched) You cannot use antibodies against your antigen own antigen. A (linear) individuals are safe to be transfused with red cells that contain A1 antigen ISBB - LEC MATUGAS, TUGAY, EMBOSCADO, PALCO, LAMELA, APIL, DELFIN, VALDIVIA, INTING BSMLS 3I & 3J 1  A2 GENE ADSORPTION METHOD codes for lesser amounts and is less efficient in the production Makes use of serum from B individuals of transferase enzymes ○ These B individuals lack A antigens, therefore, two ○ ONLY converts linear H antigens (H1 and H2) to types of antibodies are present (Anti A1 and Anti A) become A antigen. ○ It is able to produce Anti-A1 antibodies (IgM form) STEPS ON PERFORMING and still considered to be naturally occurring 1. Add A2 cells on serum of B px so Anti A will be adsorbed These type of antibodies is NOT REACTIVE a. Left on the plasma is the Anti A1 at body temperature compared to ABO 2. Anti A1 will be added to the red cells of A1 individuals antibodies a. Agglutination reaction indicates px has A1 phenotype Activates the complement at 37 degree celsius/body temperature regardless of NOTE: their form – may it be in IgG or IgM form Adsorption is commonly done if px is A and wanted to find out It is not considered as clinically significant if the px is in A1 or A2 phenotype A2 individuals tend to ONLY HAVE A antigen present on red Finding out if px is A1 or A2 is NOT ROUTINELY performed cells ○ Since they don't have A1, they are able to produce USE OF PLANT LECTIN – Dolichos biflorus antibodies – Anti-A1 antibodies in IgM form Lectin has Anti A1 specificity, thus, its reaction is like Anti A1 Although clinically insignificant in blood transfusion, IgM is antibody REACTIVE at room temperature. Lectin refers to seed extracts that agglutinate human cells with ○ Therefore, a presence of Anti A1 IgM antibody on the some degree of specificity plasma/serum of px during blood typing of cross ○ The specificity of A1 antigen is for Dolichos biflorus is matching, it is going to cause a lot of discrepancies for A1 antigen REMEMBER: Anti-A1 antibodies in IgM form is not reactive at normal A SUBGROUPS body temperature (37°C) but reactive at room temperature (25°C) BLOOD GROUP ANTIGEN PRESENT ANTI-A ANTI-A1 LECTIN A1 A1, A POSITIVE POSITIVE A2 A POSITIVE NEGATIVE Table represents the difference of A1 and A2 individuals based on its reaction with anti-A and the use of the anti-A1 lectin. Refer to the table above: Group A1 Individuals ○ You have two antibodies in A1A, so if you’re going to place anti-A it will cause an agglutination reaction mainly because it also has the linear A antigen. Figure: Representation of antigens formed for A1 and A2 phenotype ○ If you are going to use dolichos biflorus to determine the presence of A1 antigen, it will have a positive SUMMARY ON DIFFERENTIATING A1 AND A2 reaction because these individuals tend to have A1 antigen(branched A antigen) on their red cells. Group A2 Individuals ○ If you place anti-A on the red cells, it will give a positive reaction. ○ But if you test the red cells using anti-A1 lectin (dolichos biflorus), it will give a negative reaction because A1 is lacking on the red cells. WEAK A SUBGROUPS CHARACTERISTICS: Decreased number of A antigen sites per RBC. ○ result in a weak or no agglutination when tested with A1 A2 the common anti-A antibody Antigen Varying degrees of agglutination by human Anti-A,B. A1 (Branched ) and A present on A (Linear ) antigen ○ Human Anti-A,B (Linear ) antigen the RBC An antibody taken from the plasma of the A1 gene A gene “O” individual in which they tend to have Genes ✔α-3-N-acetylgalactosaminyltra ✔α-3-N-acetylgalactosami different antibodies present (e.g. anti-A, nsferase nyltransferase inherited anti-A1, anti-B, anti-A,B). converts both the branched and only converts linear H linear H antigen antigen Can be used in determining the presence of weak A subgroups Amount of Lower amount (less ○ Anti-A, Anti-A1, Anti-B, Anti-A,B High amount (more efficient) Tend to have both IgM and IgG form but coding efficient) YES Anti-B is much more identified to be in IgG Antibody NO (Anti-A1 antibodies in IgM form. production form ) Anti-AB is going to react with both A & B antigens. However, it is going to react on METHODS different antigenic sites than those that ADSORPTION were reacted with Anti-A, Anti-A1 and USE OF PLANT LECTIN (Dolichos biflorus): Anti-A1 specificity Anti-B. ISBB - LEC MATUGAS, TUGAY, EMBOSCADO, PALCO, LAMELA, APIL, DELFIN, VALDIVIA, INTING BSMLS 3I & 3J 2  It is commonly utilized in order to Strong agglutination reactions with Anti-H identify the presence of weak A ○ Because most of the H antigen are not converted antigens on the red cell If not detected: AHTR(Acute Hemolytic Transfusion reactions) membranes if the blood of the ○ The problem when we are not able to identify those patient is suspected to have the individuals with the weak A subgroup it will lead to weak A subgroup. AHTR Increased variability in the detection of H antigen resulting in It is very rare in the population strong reactions against Anti-H. ○ So far, the means of identification is anti-H lectin , and ○ mainly because they have the weak subgroup so it detecting through saliva could actually be attributed by the formation of a very Example: Ax donor(weak subgroup) was mistyped as group “O” and weak transferase enzyme in which most of the H transfused to a group “O” recipient. antigens are left unconverted. Weak A subgroups have weak/no agglutination with ○ More H antigens are unconverted compared to the commercial rgts. → A antigens present are NOT detected by anti-A antisera → mistyped as Group O(absence of A & B ag / number of the A antigens that are present on RBC in presence of Anti-A, Anti- A1 & Anti-B) which when Anti-H is applied, it is going to form a However, the Ax donor still has LITTLE amount of A antigen and strong reaction. could react with the Anti-A present in “O” individual = hemolytic Presence or absence of Anti-A1 in the serum. reactions Order of number of A antigens, in decreasing order: ANTIGEN SITE IN THE RBC ○ (most) A1 → A2 → A3 → Ax → Ael (fewest) A1 810K-1.17M A (Ag) A2 240K-290K A (Ag) WEAK A SUBGROUPS REACTIONS A3 35K A(Ag) Ax 4,800 A (Ag) AM 700 A (Ag) A1B 460-850K A(Ag) A2B 310-560K A(Ag) *Aend,Ay,Ael, Comparison on the different subgroups based on the amount of antigens that is present on the RB Ranked based on the number of antigens: ○ A1 and A2 → major subgroups A1 → highest because it has 810k.1.17M antigens approximately on the rbc ○ A3→ most common weak A subgroup d/t it having the lowest number of antigens in the rbc; therefore, Mf- mixed field agglutination reaction less detected by the common anti-A antibody. ○ agglutination pattern in which a population of the Much more identified using an anti-AB RBC agglutinated, while the remainders are antibody. un-agglutinated Occurs at