Blood Bank Immunology

Primary mission of transfusion services?

Deliver safe, compatible blood components.

Why prevent incompatible exposure?

To avoid hemolytic transfusion reactions (HTRs).

Two main units in transfusion services?

Donor collection and hospital blood bank.

Who regulates blood as a biologic/drug in the U.S.?

FDA.

Who accredits and sets standards?

AABB.

Who gives global guidance on blood systems?

WHO.

Who oversees blood-related policy in the EU?

European Commission.

Where are ABO genes located?

Chromosome 9.

What do A and B alleles encode?

Functional glycosyltransferases.

What does the common O allele encode?

Nonfunctional (amorph) transferase.

Which gene makes the H scaffold?

H gene (FUT1) on chromosome 19.

What sugar does FUT1 add?

L-fucose to type-2 chains (H substance).

Why is H required for A/B expression?

A/B sugars attach onto H.

Which sugar defines A antigen?

N-acetyl-D-galactosamine.

Which sugar defines B antigen?

D-galactose.

What surface structure defines type O?

H only (no A/B sugars added).

Which two genes define Rh?

RHD and RHCE.

Why is D antigen clinically critical?

Anti-D can cause HTRs and HDFN.

What indicates a positive serologic test?

Hemagglutination.

Three common test phases?

Immediate spin, 37 °C, AHG (Coombs).

How are reactions graded?

0 to 4+.

Core goal of pretransfusion testing?

Prevent serologic incompatibility.

Three baseline tests before transfusion?

ABO, Rh(D), antibody screen.

What else must donor units have?

Required infectious disease testing.

What does forward typing test?

Patient RBC antigens.

Reagents used in forward typing?

Commercial anti-A, anti-B (± anti-A,B).

What does reverse typing test?

Patient serum antibodies.

Cells used in reverse typing?

Known A, B, O reagent RBCs.

Typical conditions for reverse typing?

Room temperature (slide/tube or instrumented).

What does routine Rh typing detect?

Presence/absence of D antigen.

Antibody reagent for Rh test

Commercial anti-D.

Purpose of the antibody screen

Detect unexpected clinically significant antibodies.

Phases often used in the screen

IS, 37 °C, AHG.

What triggers antibody identification

Positive antibody screen.

What changes in antibody identification

Use larger RBC panels to pattern the specificity.

What's done once an antibody is identified

Select antigen-negative donor units.

Rh antigens commonly represented

D, C, E, c, e.

Kell/Kidd/Duffy examples

K/k, JkI/JkI, FyI/FyI.

MNS and others often included

M, N, S, s, P1, Lewis.

Why antigen-type a patient or donor

To determine presence/absence of specific RBC antigens.

What reagents are used for typing

Commercial antisera against target antigens.

What is tested in a crossmatch

Patient serum vs donor RBCs.

Why perform a crossmatch

Confirm compatibility before issue.

Which phases can a serologic crossmatch include

IS, 37 °C, AHG (as indicated).

When is electronic crossmatch allowed

When strict criteria are met (e.g., negative screen, history reviewed).

What equals compatibility

No agglutination/hemolysis.

What equals incompatibility

Any agglutination/hemolysis.

Universal RBC donor group

O negative.

Universal RBC recipient group

AB positive.

Name hepatitis tests on donor blood

HBsAg and anti-HBc; NAT for HBV may be included per policy.

Name HIV/HCV testing modalities

Serology (e.g., HIV Ag/Ab, anti-HCV) and NAT for HIV/HCV.

Other required infectious tests commonly performed

Syphilis; HTLV-I/II (per jurisdictional standards).

Two broad categories of reactions

Infectious and immune.

Define FNHTR

Febrile non-hemolytic transfusion reaction.

Define AHTR vs DHTR timing

AHTR

What is TRALI

Transfusion-related acute lung injury.

What is TACO

Transfusion-associated circulatory overload.

Why is accurate ABO the #1 safety priority

ABO-incompatible transfusion can be rapidly fatal.

What confirms safe unit selection after ID'ing an antibody

Crossmatching antigen-negative units with patient serum.