Antibody Screening and Identification

Flashcards for the antibody screening and identification lecture notes.

Antibody Screening and Identification Importance

Detection and identification of antibodies against red blood cell antigens is critical in pre-transfusion testing.

Antibody Screening and Identification Tool

Principal tool for investigating potential hemolytic transfusion reactions and autoimmune hemolytic anemias (AIHA).

Antibody Screening and Identification Aid

Aids in detecting and monitoring patients who are at risk of delivering infants with HDFN.

Antibody Screening Focus

Detect unexpected/irregular antibodies.

Antibody Screening

Involves the reaction between patient serum or plasma with screening cells.

Antibody Screening Purpose

Purpose is to detect RBC unexpected alloantibodies other than the expected anti-A and anti-B.

Antibody Screening Method

Indirect antihuman globulin test/ (IS phase, 37C, AHG phase; uses monospecific anti-IgG AHG reagent).

Screening cells (RBC reagents; 2-3 screening cells) Composition

Group O cells, each with a unique combination of clinically important RBC antigens, comprised of two (R1R1 and R2R2) or three (R1R1, R2R2, rr).

Each set of screen cells is

Accompanied by an antigen profile sheet/antigram.

Homozygous

Antigen expression is from an individual who inherited only one allele at a given genetic locus.

Heterozygous

Antigen expression is from an individual who inherited two different alleles at a given genetic locus.

Common Blood Group Systems With Antibodies That Exhibit Dosage

Rh (except D), Kidd, Duffy, MNSs, Lutheran.

Gel Method

Usually a microtubule filled with a dextran acrylamide gel (contains anti-IgG).

SOLID PHASE ADHERENCE METHOD Principle

RBC antigens coat microtiter wells rather than being present of intact RBC’s.

Positive result in SOLID PHASE ADHERENCE METHOD

Diffuse pattern (indicator cells react with antibodies bound to antigens in the microtiter well).

Negative result in SOLID PHASE ADHERENCE METHOD

Indicator cells form a pellet in the bottom of the well.

Antibody Identification

Done when the antibody screening test is positive to identify the alloantibody.

Antibody Identification Uses:

Panel cells (Group O, extended screening cells 11-20 cells); also comes with an antigen profile sheet/antigram.

Patient's history relating to race

Race: some antibodies are associated with a particular race (anti-Fya; Blacks; anti-U: Africans).

Patient's history relating to transfusion and pregnancy

Transfusion and pregnancy: exposure can cause production of immune antibodies.

Patient's history relating to medications

Medications: IVIG, RhIg, anti-lymphocyte globulin may transfer passive antibodies (anti-A, anti-B, and anti-D).

SELECTED PANEL CELLS

Additional panel cells that are added to help in identifying antibodies.

ENZYMES

Treating the panel cells with enzymes may help separate the specificities and allow antibody identification.

Examples of Enzymes

Ficin, papain, bromelin, trypsin.

NEUTRALIZATION

Other substances in the body and in nature have antigenic structures similar to certain RBC antigens.

SOURCE OF NEUTRALIZING SUBSTANCE of Anti-P1

Hydatid cyst fluid, pigeon droppings, turtledoves egg whites.

SOURCE OF NEUTRALIZING SUBSTANCE of Anti-Lewis

Plasma/serum, saliva.

ADSORPTION

Antibodies may be removed or adsorbed from serum by incubating the specimen with the corresponding antigen, thus allowing the antibody to bind to that antigen.

AUTOADSORPTION

Removal of autoantibodies (warm: serum is adsorbed at 370C; cold: adsorbed at 40C).

ELUTION

Used to remove, concentrate, and purify antibodies from RBC’s.

Eluate

Diluent where removed antibodies from RBC’s are harvested and tested against panel cells.

Total elution

Antibody is removed from RBC’s and the RBC antigens are destroyed (antibody id).

Partial elution

Antibody is removed but RBC antigens remain intact (RBC phenotyping and used for autoadsorption techniques).

ANTIBODY TITRATION

Done to determine the relative amount of antibody in the serum.

TYPING OF IMMUNOGLOBULIN

Uses sulfhydryl reagents which inactivates IgM leaving IgG intact.