BLOOD-GROUPS-AND-SEROLOGIC-TESTING

Immunohematology Overview

Key Concepts

  • Immunohematology involves the study of blood group systems and their clinical significance.

Dosage Effects in Blood Group Systems

  • Dosage effect definition: Greater agglutination and reactivity occurs with homozygous genes.

  • Common blood groups that demonstrate the dosage effect:

    • Rh other than D

    • MNS

    • Duffy

    • Kidd

  • Examples of related antibodies:

    • Anti-Jka and Anti-Jkb (Kidd)

    • Anti-Fya and Anti-Fyb (Duffy)

    • Anti-M and Anti-N (MNS)

Blood Group Systems and Their Relevance

Resistance to Malaria

  • Blood group associated with resistance to P. vivax malaria:

    • Duffy blood group.

Common Antibodies in Blood Banking

  • Most common antibody after ABO and Rh:

    • Anti-K (Kell).

  • Clinical Implications:

    • Anti-Fya may cause hemolytic transfusion reactions.

Autoantibodies and Their Specificities

  • Patients with paroxysmal cold hemoglobinuria may have:

    • Anti-P specificity.

Blood Group Learning Outcomes

  • Understand hypersensitivity concept and types:

    • Four Types of Hypersensitivity:

      1. Type I: Anaphylaxis

      2. Type II: Cytotoxic Reaction

      3. Type III: Immune Complex Reaction

      4. Type IV: Delayed-Type Reaction

  • Examples of clinical manifestations for each type.

Learning Assessment Summary

  • Time Allocation:

    • Various minutes allocated for explanations, assessments, and engagement activities.

  • Learning Outcome:

    • Knowledge acquisition about blood group systems, antibodies, and reaction types.

Specific Antigen and Antibodies Characteristics

Lewis System

  • Lewis antigens found on type 1 glycosphingolipids, not intrinsic to RBCs.

  • Lewis antibodies: Usually IgM, naturally occurring; significant in pregnancy.

MN Antigens

  • Present on glycoprotein Glycophorin A; easily destroyed by enzymes.

  • Anti-M antibody: Cold-reactive saline agglutinin; rarely causes severe reactions.

Kell Antigens

  • Highly immunogenic; implicated in hemolytic transfusion reactions.

  • Common Anti-K antibody is rare and significant.

Duffy and Kidd Systems

  • Duffy: Antigens protect against P. vivax.

  • Kidd: Associated with hemolytic transfusion reactions, particularly delayed types.

Minor Blood Group Systems

Diego System

  • Composed of antigens (Dia/Dib) expressed on RBCs, resistant to certain enzyme treatments.

Indian System

  • Includes antigens (Ina/Inb) and has low prevalence in various populations.

Dombrock System

  • Diverse phenotypes; clinically significant in HTRs but not significant for HDFN.

Chido/Rodgers System

  • Antigen sensitive to destruction by enzymes, typically considered clinically insignificant.

Gerbich and Cromer Systems

  • Gerbich System: Low prevalence; can cause mild HDFN.

  • Cromer System: Null phenotype is rare; antibodies cannot cause HDFN.

Knops and Indian Systems

  • Positioned on complement receptors with varying expressions based on genetic factors.

Oka System and Raph System

  • Oka antigen expresses well at birth; Raph’s clinical relevance is currently unclear.

The Latest Systems: RH-Associated Glycoprotein

  • Expresses Rh antigens and is linked with various phenotypes.

Clinical Application Implications

  • Understand unexpected antibodies' impact on transfusion.

  • Knowledge of antibody types and their significance aids in blood compatibility decisions.