chapter 4 Flashcards

Question

Lewis antibodies

Answer 1

lewis antibodies are usually IgM, react best at room temperature & occasionally bind compliment, which results in vitro hemolysis No lewis antibodies are produced by people whose RBC type is Le(a-b+) because their body fluids contain both lewis structures People who type Le(a+b-) can produce anti-Le^b people who are Le( a-b-) can produce anti-Le^a &/or anti-Le^b anti- Le^bH can be produced by people whose RBCs lack Le^b & have a small amount of H antigens - A1 cells Le( a+b-)

Answer 2

the presence or absence of A, B , H , Le^a &/or Le^b antigens in saliva can be determined using the saliva inhibition test saliva is collected from the patient and incubated with suitable diluted anti-A, anti-b, anti-H , anti-Le^a & anti-Le^b, each in separate tubes if present it will bind to the antibody then cells with the corresponding antigens are added to each tube if there is no agglutination, the antibodies added have already bound to the antigens in the persons saliva ( meaning they are positive for that antigen ) if there is agglutination, the antibodies didn't have an antigen to bind to originally so they can bind to the regent cell added in the last step if agglutination occurs in all tube of ABO( negative results ) this person is a non secretor & therefore ABO is unknown if agglutination overs in both lewis cells tubes ( negative results) this person is lewis negative & therefore secretor status is unknown

Answer 3

controls must be run to ensure the procedure worked as expected, the antisera worked as expected & the dilution didn't cause ant of the negative results this usually includes a Dilution control tube * - containing the diluted regent, appropriate RBCs & saline - a positive control tube should contain diluted regent, appropriate RBCs & the saliva of a known secretor the dilution control tube should be neg( agglutinate ) the positive control tube should be pos ( no agglutination)

Answer 4

bombay phenotype results from hh & sese genotypes. These people lack H substance both on their RBCs & in their secretions they will lack A& B antigens, regardless of their ABO genotype, in both as well since there is no H precursor during ABO testing a bombay will appear as a group O during antibody testing bombay will produce an anti-H that reacts with all RBCs except those of bombay phenotype therefore the plasma of a bombay person will react with screening cells that are typically group O

Answer 5

some people appear bombay but have very small amounts if A &/or B antigen on their RBCs their genotype is hh but they possess at least one Se gene the Se gene produces fucosyltransferase that acts on type 1 precursor substance in secretions, this type 1 H substance formed from the Se gene can convert to A or B antigens para-bombay will have ABH antigens in their secretions & plasma sometimes they will have small amounts of AB &/or H antigens that have absorbed onto their RBCs from their plasma they will possess a weak reaction & they only have type 1 antigens (absorbed) not intrinsic type 2 antigens type 2 requires the H gene

Answer 6

Bombay will make a naturally occurring anti-H as well as anti-A, anti-B & anti-A,B Anti-H is an IgM that reacts strongly at 37 degrees can cause intravascular hemolysis Parabombay will make H substances in they secretions & wont produce anti-H

Answer 7

there are 2 carbohydrate antigens I & i at both i antigen is expressed on RBCs most is converted to I in the firth 18 months antibodies in this system are usually IgM autoantibodies auto anti-I is a common cold autoantibody - reactivity can increase due to Mycoplasma pneumoniae - clinically significant anti -I may be detected in adults who have not converted i antigen detection of anti-i has been associated with infectious mononucleosis

Answer 8

Cold auto agglutinins that react at room temp or lower & react with H ( anti-H ) or anti I&H ( anti-IH) are relatively common & insignificant - these are different than the Bombay anti-H which are highly significant anti-H or anti-IH an be found in the plasma of para-bombay people but much more commonly in patients of the A1 or A1B phenotype bc A1 have the least amount of H on their cells anti-IH will exhibit little or no reaction with cord cells bc they have i and no I antigen. anti -IH will react strongly with O cord cells ( bc of H antigen)but not at all with A cord cells

Answer 9

O> A2 > B > A2B > A1 > A1B

Answer 10

consist of 2 parts : 1. testing for antigens on RBCs ( forward grouping ) - combining unknown patients cells with know reagent antibody 2. testing for antibodies in plasma ( reverse grouping ) - combining unknown patients plasma with known ABO cells

Answer 11

usually involve forward & reverse reactions not agreeing. mixed field, or obtaining different results from past results are also discrepancies when identifying discrepancies, weak reactions are more likely to be aberrant than strong ones ( look at weak reactions to find answers)

Answer 12

the patient is a subgroup of A or, less frequently, a subgroup of B . The very rare cis AB genotype ( both A& B gene are on the same chromosome with no ABO gene on the other) may also result in a weak expression leukaemia or other malignancies may result in alterations of th A or B antigen on the RBCs. they wont react normally with antisera Some people have excessive amounts of soluble A &/or B antigen in their plasma. if plasma suspended cells are used the antigens in the plasma can neutralize the reagent antiserum, resulting in days - neg reaction ( using washed cells avoids this )

Answer 13

modifying test; extended room temp or 4 degree incubation, enzyme rating the patients cells ( as ABO antigens are enhanced by enzymes) saliva inhibition test may be used ( if patient is a secretor ) genetic analysis can be performed

Answer 14

when sample has 2 different cell populations most often caused by transfusion with non-ABO identical cells most commonly a non group O patent is given an emergency transfusion of group O cells ( to avoid intravascular hemolysis) other causes: ABO non identical bone marrow or hematopoietic progenitor transplant weak ABO subgroups such as A2 Chimersim - fraternal twins exchange blood- forming cells in utero or when 2 different populations of cells ( donor & recipient ) reside together in the bone marrow after transplantation mosaicism -occurs when 2 sperm fertilize 1 egg ( dispermy) resulting in 2 distinct cell populations mixed field due to chimerism & mosaicism exist throughout patients life & are considered self, so ABO antibodies aren't made towards them

Answer 15

discrepancies in the reverse group are less common the first step when seeing a discrepancy in the reverse is to check the patients age -if the patient is younger than 4 month the patient shouldn't be tested fro reverse bc they haven't developed antibodies yet - elderly also exhibit decreased antibody concentrations other reasons for discrepancies : - ABO antibodies may be diluted to a non detectable level if the patient has received therapeutic plasma exchange therapy - patients who are on aggressive immunosuppressant therapy can have decreased expression of there antibodies - patient who has a non identical ABO bone marrow transplant - certain diseases such as agammaglobulinemia, hypogammaglobulinemia,& some leukemias & lymphomas

Answer 16

serum/cell ration : in a tube testing, add 1-2 additional drops of patient/donor plasma can sometimes enhance a weak reaction temperature : ABO antibodies are IgM & are generally cold -reactive. the reverse can be incubated for 15-30mins at room temp. if that doesnt resolve it , the temp can be lowered to 4 degrees, where group O cells & an auto control should be tested as well to control for the presence of other cold antibodies enzymes: proteolytic enzyme treatment of the reverse grouping cells can soemtimes enhance a weakly reactive ABO antibody. can be done using ficin ( fig), papain ( papaya ) bromelin ( pineapple) or trypsin(hogs stomach) controls of group O & autologous cells should be enzyme-treated & tested at the same time to ensure any reactivity is due to ABO antibodies