Other Blood Groups PDF

# 4.1 Lewis Blood Group System ## Lewis System Characteristics - How is the Lewis Blood Group System unique? - Its Ags are not synthesized by RBCs, the Ags are on Type 1 glycosphingolipids that are passively adsorbed onto the RBC membrane in the plasma. - What are the 2 main Ag in the Lewis BG...

# 4.1 Lewis Blood Group System ## Lewis System Characteristics - How is the Lewis Blood Group System unique? - Its Ags are not synthesized by RBCs, the Ags are on Type 1 glycosphingolipids that are passively adsorbed onto the RBC membrane in the plasma. - What are the 2 main Ag in the Lewis BGS? - Leª (LE1) and Leb (LE2). - What are the 3 common phenotypes of the Lewis BGS? - Le(a+b-), Le(a-b+), and Le(a-b-). - Are Lewis BGS Ag Leª (LE1) and Leb (LE2) antithetical (opposite) Ag? - No, it was thought that Leª (LE1) and Leb (LE2) were antithetical (opposite) Ag, but we now know this is not so because they do not result from alternative alleles of a single gene. - How are Lewis BGS Ag Leª (LE1) and Leb (LE2) encoded? - They result from the interaction of 2 fucosyltransferases encoded by independent genes, *Le* and *Se*. - What is a fucosyltransferase? - An enzyme that transfers an L-fucose sugar from GDP-fucose (guanosine diphosphate) donor substrate to an acceptor substrate. - What type of Ag are Lewis BGS Ag Leª (LE1) and Leb (LE2) and how are they acquired? - The Ag are glycolipids (type 1 chains) acquired by adsorption of the soluble Ag from the surrounding plasma onto RBCs. - What makes Lewis BGS Ag unique from other BGS? - They are not manufactured by the red cell. - How are Lewis BGS Ag Lea (LE1) and Leb (LE2) eluted from red cells? - Eluted (removed) after transfusion or by increases in plasma volume and increased circulating lipoproteins. - Where are Lewis BGS Ag Leª (LE1) and Leb (LE2) produced? - By tissue cells and found primarily in plasma and body secretions like saliva or tears as soluble Ag and glycoproteins. ## Lewis Phenotypes in secretions and *Se* - What do the 3 Lewis phenotype represent? - The presence or absence of Lewis and secretor enzymes. - Where is the *Se* (secretor) gene located? - Chromosome 19. - What are the 2 alleles at the chromosome 19 locus? - *Se* and *se*. - What kind of gene is *se*? - An amorph (*sese*) that produces no detectable product in secretions. - How are the enzymes produced by the *Se* and *H* genes alike and how are they different? - The enzymes produced by the *Se* and *H* genes are the exact same (because they are fucosyltransferases), except the *H* gene enzyme adds the sugar L-Fucose to Type 2 precursor chains (RBC membranes), while the *Se* gene enzyme adds the sugar L-Fucose to Type 1 precursor chains (fluids). - *Se* adds L-Fucose to Type 1 precursor chains, which are fluids. - *H* adds L-Fucose to Type 2 precursor chains, which are RBC membranes. - What genotypes are referred to as secretors? - Individuals with a secretor genotype (homozygous *SeSe* or heterozygous *Sese*). - What genotype are non-secretors? - Individuals with only the *se* gene (homozygous *sese*). - What are in *sese* individuals' secretions? - They fail to produce ABH Ag in their secretions. ## The Lewis Gene - Where is the *Lewis* gene and what genes is it closely linked to? - *Lewis* gene is closely linked to *Se* (FUT2) and *H* (FUT1), which are all located on chromosome 19. - Le Fut3, Se Fut2, HFut1; secretors - Fut3 will modify HFut1 Ag to create Leb; non-secretors - Fut3 Leª is formed by the addition of a fucose residue to the HAg [link](https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.bloodjournal.org%2Fcontent%2F122%2F21%2F3848&psig=AOvVaw1_X9I_pO7C6L23d8nRk8Vq&ust=1670599300537000&source=images&cd=vfe&ved=0CA8QjRxqFwoTCIiP1aL0-PoCFQAAAAAdAAAAABAD). ## Lewis Phenotypes ### Le(a+b-) - How is this phenotype produced? - This phenotype is caused by inheriting the *Lewis* gene (LE or FUT3) but not the *Secretor* gene (SE or FUT2). - When are Le and H Ag produced? - When *Le* and *H* genes are present. - What is the genotype of their *Se* gene? - The *Se* gene is absent so the genotype is *sese*. - What is the phenotype of their *Se* gene? - Non-secretors of A,B,H Ag. - What do Le(a+b-) individuals have in their secretions? - Leª. ### Le(a-b+) - How is this phenotype produced? - This phenotype is caused by inheriting both the *Lewis* (Le) gene and the *Secretor* (Se) genes; Le, H, and Se genes are present. - Which Ag are produced? - Leª (LE1) and Leb (LE2) are produced; Le makes Leª (LE1) and Le/Se makes Leb (LE2). - What are the secretions in this phenotype? - A, B, H, Leª (LE1), and Leb (LE2). - What Ag will be present on the RBC surface? - A, B, H, and Leb (LE2). ### Le(a-b-) - How is this phenotype produced? - This phenotype is caused by not inheriting the *Lewis* gene (lele). - Do Le(a-b-) secretors have the *Secretor* gene / what are in their secretions? - Le(a-b-) secretors have the *Se* gene to add fucose to the RBC chain, so A, B, H Ag are present in secretions. - What do Le(a-b-) non-secretors have in their secretions? - Nothing in their secretions. ### Le(a+b+) - What is in their secretions? - None. - Significant? - No. ## Characteristics of Lewis Ags and Abs ## Development and Changes of Lewis Ags after Birth - Describe the development of Lewis Ags - Lewis Ags are not well developed at birth, but begin to appear shortly thereafter because the Ags must be adsorbed onto the red cells. - What is the phenotype of cord blood and newborns? - Le(a-b-). - What is the phenotype of individuals with the *Le* and *sese* genotypes? - Lewis Ags are not detectable on cord cells, but the infants secrete Leª in their saliva. - When are Lewis glycosphingolipids detectable in plasmas? - After approximately 10 days of life. - If you follow transformations from birth to 10 days after life, when will the true Lewis phenotypes result? - After 6 years of age. ## Pregnancy and Lewis Ags - What is the strength of the Lewis Ag during pregnancy? - Strength may decline dramatically during pregnancy. - What is not uncommon for pregnant females regarding the Lewis Ag? - To make transient Lewis Ab. - What is believed to affect the distribution of Lewis glycolipid between plasma and RBCs? - Physiological changes in the composition of blood during pregnancy. ## The Lewis System Abs - What Abs do secretors with Le(a-b-) produce and have circulating in their serum? - anti-Leª, anti-Leb. ## Anti-Leª - Where is Anti-Leª found? - Commonly found in the serum of prenatal patients. ## MNS Blood Group System - Genes of the MNS BGS? - *GYPA*, *GYPB*. - Phenotypes of the MNS BGS? - M+N- - M+N+ - M-N+ - What are the S and s Ag? - Distinct from M and N, but they are genetically linked. - Phenotypes of the S - S+s- - S+s+ - S-s+ - S-s-U- ## MNS System Abs ## Anti-M - What kind of antibody is anti-M? - Cold agglutinins (optimally reactive at 4C); weakly reactive or not at all at 37C IgM and rarely clinically significant. ## Anti-N - How often is Anti-N found? - Rarely found. - What kind of antibody is Anti-N? - Cold reactive IgM; clinically insignificant unless, very rarely reacts at 37C. ## Anti-S and Anti-s - What kind of Abs are these? - Uncommon, usually _IgG_ and immune in nature; optimally reactive at 37C and will usually react through the antiglobulin phase. - Are they clinically significant? - Both are usually considered to be clinically significant, bind complement, and have been associated with severe HTRs, and have caused HDFN. ## Anti-U and other GPA- and GPB- deficient phenotypes - When is the Anti-U produced? - S-s-U- phenotype. - What kind of Ab is Anti-U? - A rare Ab that reacts with the cells of most people (high frequency Ag). - What Ab class is Anti-U? - _IgG_ in nature. - What temperature does Anti-U optimally react? - 37C. - Does Anti-U bind complement? - No. - What makes Anti-U clinically significant? - Has been associated with severe hemolytic transfusion reactions (death) and HDFN. - If an individual has Anti-U, what must you do to find a donor match and why? - Because the U Ag is present in nearly 100% of the population, it may be necessary to consult the AABB Rare Donor Registry for assistance in obtaining suitable units for transfusion; there are <10 U negative individuals in the US. ## Properties of M, N, S, s and U Abs - What are the properties of anti-M and anti-N? - Naturally occurring - Cold _IgM_ - Shows dosage - Clinically insignificant - What are the properties of anti-S, anti-s, anti-U? - Requires exposure - Warm _IgG_ - Shows minimal dosage - Clinically significant ## P (003) and Globoside (028) Blood Group Systems ## Characteristics of the P and Globoside - What Ags are assigned to the P1PK blood group system? - P1 and Pk. - What Ags are assigned to the Globoside BGS? - P. - What are high incidence Ags of this system that can be found on more than 99% of the population? - P1, P, Pk, P2. - How are P1, P, Pk, P2 synthesized?"? - The sequential action of glycosyltransferases, which adds sugars to precursor substances. - Which Ag are found on lymphocytes, monocytes, granulocytes, and RBCs? - P1, P, Pk. - Which Ag can be found on plts, epithelial cells, and fibroblasts? - P. - What are the possible phenotypes? - P1, P2, P, P1, P2k. ## P Ag - Which chromosome are P Ag found? - 3. - What is the P Ag responsible for? - Production of transferase which transforms Pk Ag into the P Ag. ## P1 Ag - What BGS is P1 a part of? - P1PK BGS (003). - What is the most common Ag in the P BGS? - P1 Ag. - What is the expression growth of P1 Ag? - Poorly expressed @ birth and may take up to 7 years to be fully expressed. - How can P1 Ag expression be inhibited? - Expression can be inhibited by a rare dominant gene, *in(lu)* which will result in Lu(a-b-) RBCS. - If P1 is inhibited in a rare way, how will they type? - Luther BGS may inhibit P1 expression, causing P1 individuals to type as P1 negative. - Where can P1 Ag be found?"? - In individuals with a hydatid cyst infection AKA *Echinococcus granulosus*-tapeworms. ## P Blood Group System Ab ## Anti-P1 - What kind of ab class is Anti-P? - _IgM_. - Which individuals will have Anti-P? - Found in serum of individuals who are P2-. - What temps do Anti-P1 normally react? - 4C. - Is Anti-P1 clinically significant? - It is clinically insignificant unless detected at 37C. - When Anti-P1 reacts at 37C, what can it cause? - Both immediate and delayed HTRs. ## Anti-P - What individuals will express Anti-P? - Found in the serum of Pk individuals. - Is it clinically significant? - Yes, it is a clinically significant _IgG_. - If an individual has anti-p, what must they be transfused with? - P negative RBCs. - What can Anti-P cause? - Spontaneous abortions in both p and Pk females. - What class of Ab is Anti-Pk? - Clinically significant _IgG_. ## Anti-P+P1+Pk - Who makes Anti-P+P1+Pk Ab? - All 3 P/GLOB system AB are found in p individuals. - Which portion can bind complement efficiently and what can that cause? - Anti-P portion, causing severe HTRs in p individuals. - Which portion can cause HDFN in p individuals? - Anti-P and Anti-Pk. ## Ii BGS ## Relationship of I Ag to the i Ag - Describe the expression of li - Developmentally regulated and expressed in a reciprocal relationship. - Explain who has I and i - All human red cells both I and i, but the 2 Ag are present in varying amounts at different stages of development. - What are cord RBCs rich in? - i Ag, have little or no I Ag. - When does I Ag gradually develop? - During the first 2 years of life. ## Anti-l - What class of Ab is Anti-I? - _IgM_ and strongly reactive at 4C. - When does Anti-l exist? - Most often as an autoantibody, in I positive people (associated with cold agglutinin disease, Mycoplasma pneumonia infection) - What in vitro testing does Anti-I commonly interfere with? - Compatibility testing - Anti-l reacts with all pt red cells. - Ab studies - Ab screen and ID results in false positive since most red cells contain I Ag SO false positives may mask the presence of a potential significant Ab. - ABO reverse grouping if done at 4C. - What is the major concern regarding anti-l? - It may be masking the presence of other significant Ab. ## Anti-i - Is it a common Ab? - No, it is a fairly rare Ab, usually an autoAb. - When will Anti-i be seen? - Infectious mononucleosis - Myeloid leukemia - Alcoholic cirrhosis - Reticulosis ## The Kell and Kx BGS ## Intro - What are the 2 major alleles and Ag - The K and k are the 2 major alleles, which produce K and k Ag respectively. - What are other Kell Ag and where do they come from? - Kpa, Kpb, Jsa, Jsb arise from alternative alleles. - What are the genes and proteins in the Kx BGS? - XK gene is responsible for Kx protein and is located on the X chromosome (only expressed in males). - What is covalently linked to the Kell glycoprotein? - Kx protein. - What is essential for the Ag of the Kell system to be expressed normally on red cells? - The Kx system. ## General Characteristics of Kell System Ag - Are they present at birth? - Well developed at birth. - What is unique about the Kell Ag? - Not denatured by routine Blood Bank enzymes: ficin, papain. ## Kell system Ag types - What are the Ags? - K, k, Kpa, Kpb, Jsa, Jsb. - What is important about K Ag? - Considered to be a powerful immunogen, 2nd only to D Ag in its potential to induce alloimmunization (production of Ab against a non-self Ag) ## Ko (Kell null) phenotype - How is this phenotype inherited?"? - Results from the inheritance of 2 rare Ko genes. - What do their red cells have? - Red cells lack all Kell system Ags but express large amounts of Kx Ag. ## Kell system Abs ## Anti-K - What is significant about Anti-K? - After ABO and Rh Abs, anti-K is the most common clinically significant Ab seen in the Blood Bank. - What class of Ab is Anti-K? - Usually _IgG_ in nature. - How do Kell Ab appear? - produced bc of the red cell transfusion or pregnancy. - When is it usually detected? - 37C and AHG phase of testing. - Is it clinically significant? - Yes and has been associated with severe HTRs and HDFN. ## Anti-k, anti-Kpa, anti-Kpb, anti-Jsa, anti-Jsb - How are Ab to low frequency Ag often detected? - Through unexpected incompatible crossmatches AKA Ab not identified in screen, but final crossmatch agglutinates. - What are the low frequency Ag? - Kpa and Jsa. - Which Ag are high frequency? - k, Kpb, Jsb. - Which Ab are rare and why? - Ab to high frequency Ag (anti-k, anti-Kpb, anti-Jsb) are rare because so few people lack the Ag. ## The Duffy (008) BGS ## Ag and possible phenotypes of the Duffy BGS - What are the Ab? - Anti-Fya and Anti-Fyb. - What are the Ag? - Fya and Fyb. ## Fy gene - What does the Fy gene play a role in? - Susceptibility to red cell invasion by Plasmodium vivax, the causative agent of malaria. - Cells that are Fy(a-b-) and lack the Fy6 receptor are resistant to malaria invasion. ## Duffy system Ag - What are the Duffy BGS Ag? - Fya, Fyb, Fy3, Fy4, Fy5, Fy6. - What Ag are well-developed at birth? - Both Fyª and Fyb Ag. - How are Duffy Ags destroyed? - By routine BB proteolytic enzymes like ficin, papain, bromelin. ## The Fy(a-b-) phenotype has different genetic origins - Fy(a-b-) individuals of African ancestry also express what Ag? - Fy4. - Fy(a-b-) individuals of non-African ethnicity express what Ag? - Fy3. ## Anti-Fya and Anti-Fyb - What class of Ab are Anti-Fyª and Anti-Fyb and when do they react best? - IgG Ab that react best in the indirect antiglobulin phase. - Do these Ab bind complement? - Capable of binding complement. ## The Kidd BGS - What are the 3 Ag? - Jka, Jkb, Jk3. - What are the main alleles? - Jka, Jkb. - What phenotypes is Jk3 present? - Jk3 Ag is present on all Jkª and Jk♭ red cells (Jkª/Jk3, Jk♭/Jk3), but not on Jk(a-b-) RBCs. ## The Kidd System Ag - How are they at birth? - Well-developed on the RBCs at birth. - Are they immunogenic? - No. - Are they destroyed by enzymes? - NOT destroyed by enzymes. ## The Kidd System Abs - What makes these Ab difficult to detect? - Both Ab deteriorate rapidly during storage. - Unlike other blood group Abs, anti-Jkª and anti-Jkb fade quickly from the individual's circulating plasma. ## Clinical Significance of Kidd Abs - What are these Ab made in response to? - Pregnancy or transfusion. - How are the Ab titers? - Titers of Anti-Jkª and Anti-Jkb gradually declines in vivo. - What do the Abs cause? - They are the most common cause of delayed HTRs. - When is the rare autoantibody-Jkª documented? - Warm Autoimmune Hemolytic Anemia. - Methyldopa (Aldomet) drug-induced hemolytic anemia. - Pts with recent viral or bacterial infections. - Pts who received medications preserved with Paraben compounds. - What does Paraben do to the Ab? - Alters the Jkª Ag causing the body to not recognize as self and make an autoAb. ## Lutheran BGS ## Characteristics - What gives rise to the various Lutheran Ag? - Amino Acid changes give rise to the various Lutheran Ag. ## Lutheran BGS Ag - What are the 2 most common Lutheran Ag?"? - Low frequency Luª Ag and the high frequency Lub Ag. - What is the Lutheran Null Phenotype? - Lu(a-b-). - How can the Lutheran Null Phenotype result? - Dominant *inLu* suppressor gene. - Recessive *LuLu* gene. - Recessive X-linked gene. ## Lutheran BGS Abs ## Anti-Lua - What class of Ab is Anti-Luª? - _IgM_. - What does in vitro testing show? - Anti-Luª often displays a characteristic loose, mixed-field during in vitro testing. - Is it clinically significant? - Most examples are not considered to be clinically significant (mild HTRs have been reported; have never caused severe HDFN). ## Anti-Lub - When is it produced? - Following transfusion or pregnancy. - What Ab class is it? - _IgG_ with optimal reactivity at 37C and the AHG phase. - Is it clinically significant? - Has been reported to cause mild cases of HTRs. ## Anti-Lu³ - When is this Ab produced? - By individuals with the rare Lu(a-b-) phenotype when due to the recessing *LuLu* inheritance. - When does this Ab react? - In the AHG phase. - Is it clinically significant? - Yes and has been reported to cause mild HTRs. ## Applications to routine Blood banking - Clinically insignificant? - M, P1, I Ab react at room temperature. - Clinically significant? - K, S, s, Fya, Fyb, Jka, Jkb Ab react in the AHG phase. # 4.2 The Antiglobulin Test ## Principle of AHGs - What are AHG's used to detect? - Bound red cell Abs that do not produce direct agglutination. - What does the antiglobulin test use? - A secondary antibody that has been made in another species, is directed against human globulins, and attaches to and agglutinates sensitized red cells. - Where are AHG's obtained from? - Immunized nonhuman species and bind to human globulins such as _IgG_ or complement and are either free in serum or attached to Ags on RBCs. - What are the practical uses of the Antiglobulin test? - Detection of RBCs that were sensitized with non-agglutinating "incomplete" Ab, _IgG_ Ab. - The antiglobulin reagent could be used to detect the sensitization of red cells with complement. - Antiglobulin can detect complement which is bound to the RBC membrane in vivo. ## Polyspecific vs monospecific AHG ## AHG reagents - How is AHG sera divided? - Into 2 classes; monoclonal and polyclonal. - How is monoclonal AHG produced? - Hybridoma technology fuses mouse spleen lymphocytes with myeloma cells. - What do monoclonal AHG produce? - An immortal cell line that produces a specific antibody directed against a single epitope. - How is polyclonal AHG produced? - Polyclonal antisera is produced by injecting animals with human globulin components and then collecting the antihuman antibodies. - What are polyclonal AHG directed against? - Sera made from animals are directed against multiple epitopes. ## Abs required in AHG - What must AHG contain? - Antibody activity to non-agglutinating blood group Abs. ## Polyspecific vs monospecific AHG - What are examples of monospecific AHG Reagent?"? - Rabbit monoclonal - _IgG_ heavy-chain specific - Monoclonal _IgG_ AHG reagents. - What are the advantages of using monospecific AHG reagents?"? - Higher titer than polyclonal sera. - What are some disadvantages of using a monospecific AHG reagent?"? - Over-specificity - Overly sensitive - Complement fixation may not initiate. - What are the examples of polyspecific AHG reagent?"? - Rabbit polyclonal - Rabbit/murine monoclonal blend - Murine monoclonal - What are the advantages of using polyspecific AHG?"? - More likely to pick up genetic variants. - Less expensive. - What are the disadvantages of using polyspecific AHG?"? - Low specificity - Low titer ## IAT and DAT ### Indirect Antiglobulin Test - What are the purposes for an IAT? - Used in the detection of incomplete (non-agglutinating) antibodies to potential donor red cells or to screening cells in serum. - Ab screen utilizes the indirect Coombs testing procedure to find the atypical Ab in the pt’s serum. - Used also in Ab detecting and ID using a panel of red cells that contain known Ag profiles. - What is the principle of IAT testing? - To detect in-vitro sensitized red cells. - How many stages is IAT? - 2 stage procedure where 1) cells are are exposed to a source of Ab such as serum or antisera then 2) Ab and or complement sensitize the RBC during an in vitro incubation phase at 37C in LISS or albumin. - The cells are then tested with the antiglobulin sera to check for sensitization. ### Direct Antiglobulin Test - What are the purposes for a Direct Antiglobulin Test? - Designed to detect antigen-antibody complexes that have formed in-vivo. - When could an Ag-Ab complex form in vivo? - Autoimmune hemolytic anemia (AIHA), HDN, Drug-induced hemolytic anemia, and HTRs. - When may a DAT be required? - As a part of the pre-transfusion testing if the pt has been transfused within the last 2 weeks, has a history of Abs, or is pregnant. - What is the principle of DAT testing? - To detect in-vivo sensitized red cells with IgG and complement components in which RBCs are mixed with antihuman globulin to determine if sensitization has occurred in vivo. - Why would we need to test for complement. ### Interpreting DAT panel - What does interpreting the significance of a positive DAT require?"? - The knowledge of the pt’s diagnosis, drug therapy, and recent transfusion therapy. ### Factors affecting the antiglobulin test - The number of IgG molecules sensitized on RBCs and the rate at which sensitization occurs can be influenced by? - Ratio of serum to cells (zonal reactions) - Reaction medium utilized: albumin, LISS, PEG - Temperature - Incubation time - Proper washing of RBCs - Proper centrifugation is necessary. - How can you get false positive results in the antiglobulin test? - Saline and glassware contaminated with silica particle or other debris and dirt. - Over-centrifugation. - Extreme reticulocytosis may cause a false positive DAT as the transferrin (a beta globulin) is attached to the retic membrane. - The antiglobulin serum may be contaminated with Rabit-Anti-Transferrin. - Cells are positive by the Direct Antiglobulin Test cannot be used in an indirect test. - Cells would always be positive no matter which serum the cells are mixed with. - Normal serum may contain cold autoab capable of sensitizing red cells with complement at refrigerator temperatures and sometimes even at room temp. - How can you get false negatives? - Inadequate washing causes neutralization of the antiglobulin reagent. # 4.3 Detection and ID of Abs ## Intro - What is the focus of Ab detection methods? - To find "atypical,” “irregular,” “unexpected” Ab. - What does the focus NOT include? - "Expected" or naturally occurring ABO Ab. - What are the unexpected Ab of primary importance? - The immune alloab, which are produced in response to RBC stimulation through transfusion, transplantation, or pregnancy. - What is critical in pretransfusion compatibility testing? - The detection of Ab directed against RBCS Ag by 1) investigating potential hemolytic transfusion rxns and immune hemolytic anemias 2) aids in detecting and monitoring patients who are at risk of delivering infants with HDFN. ## Types of Ab - What are expected Ab? - Consistent and predictable Ab and are produced by the body without exposure to RBCs; like ABO Ab. - What are unexpected Ab? - Produced in response to RBC stimulation via transfusion, transplantation, and pregnancy; other than naturally occurring Ab such as Anti-D or Lewis Ab. - What are immune Ab? - AKA alloAb bc of exposure to RBC ag that don't initially belong to an individual. - Falls under the unexpected Ab category, as they are not initially a part of the immune system. - Mostly are of the IgG type that reacts at 37C and req use of AHG reagent for detection. - What are naturally occurring Ab? - Formed bc of exposure to environmental sources, such as pollen, fungus, and bacteria, which have structures like some RBC Ag. - What are passive (acquired) Ab? - Ab produced in one individual and then transmitted to another via plasma-containing blood components or derivatives. - What are autoAb? - Abs directed against the individuals' own RBCs. - Typically agglutinate, sensitize, or lyse RBCs of most random donors as well as their own. - What are alloab? - Produced after exposure to genetically different or non-self Ag such as different RBCs after a transfusion. - What are warm Ab? - Typically, _IgG_ and react best by the indirect antiglobulin technique and do not directly agglutinate saline-suspended RBCs after 37C. - What are cold Ab? - Most encountered at 4C reaction incubation, are of _IgM_ type, and can activate complement. ## Ab screen - What does the AABB's Standards for Blood Banks and Transfusion Services require the use of an Ab screen for? - Recipients as part of pretransfusion compatibility testing. - Obstetric patients to evaluate the risk of HDFN in the fetus and to assess the mother’s candidacy for Rh-immune globulin (RHIG) prophylaxis. - Donors of allogenic blood and blood product and stem/progenitor cells. - What are the enhancement reagents for Ab detection? - 22% bovine albumin. - Low lonic Strength Solution (LISS). - Polyethylene glycol (PEG). - What is the point of enhancement reagents? - Increase the chances of agglutination. - How does LISS work? - In addition to lowering the zeta potential, LISS increases the uptake of antibody onto the RBC during the sensitization phase (AKA easier for Ab to move through LISS). - What do AHG reagents allow for? - The agglutination of incomplete Ab. - What are the advantages of the gel method? - Standardized pipetting of reagents and specimen. - Reading of agglutination rxns. - Reviewing stable reaction endpoints up to 24 hours. - Reduced specimen volume. - What are the disadvantages of the gel method? - Longer TAT for ABO determinations and less sensitive detection of ABO Ab in patient serum or plasma when compared to tube method. - Need for specific incubators and centrifuges that can accommodate gel cards. ## Screen Interpretation - What does agglutination or hemolysis at any stage of testing indicate? - The need for Ab ID studies. - Are check cells a stage of testing? - No check cells are a control. - What does evaluation of results provide? - Clues and give direction for the ID and resolution of the Ab or Abs. ## Limitation of the Ab screening test - What are the limitations of the Ab screening test?"? - When testing with a 3-cell screen and the result is negative with all 3 cells, there is a 95% chance confidence rate there are no clinically significant Ab. - The Ab screen does not detect Ab that have a titer below the level of sensitivity or Ab to low-frequency Ag. - What factors influence sensitivity? - Cell-to-serum ratio (zonal rxns). - Temperature. - Length of Incubation. - pH. # 4.4 Miscellaneous Testing ## Adsorption ## Principle of Adsorption - What is the principle of adsorption? - Adsorption is the uptake of specific Ab from the serum using known Ag. - How can autoAb be removed from the pt's serum?"? - AutoAb can be removed from the patient’s serum by using their own red cells. - How can alloAb be removed from the pt's serum?"? - AlloAb can be removed from the pt’s serum by using other cells. - How are Ab removed from serum?"? - By adding the target Ag and allowing the Ab to bind to the ag. - The Ag-Ab complex is detected by the presences of solid precipitates and is removed from the test system by centrifugation. ## Commercial Reagents for Adsorption - What is used to adsorb HLA-related Bg Ab from serum? - Human platelet concentrate. - Where are HLA Ag found? - On the plt and bind the HLA-related blood group Ab, leaving other specificities in the serum, where Ab ID can be performed. - What does Rabbit erythrocyte stroma f(x)? - Incubating with pt’s serum removes other Ab specificities that interfere