Overview
The Lewis blood group system describes Le(a) and Le(b) antigens that are synthesized in plasma and adsorbed onto red cells; corresponding antibodies are typically cold-reactive and usually considered clinically insignificant for red-cell transfusion.
Classification
| Phenotype | Classic teaching link | Antibody possibility |
|---|---|---|
| Le(a+b−) | Nonsecretor framing | Anti-Le(b) |
| Le(a−b+) | Secretor framing | Anti-Le(a) |
| Le(a−b−) | Neither adsorbed antigen | Anti-Le(a) and/or anti-Le(b) |
| Le(a+b+) | Uncommon in adults | Context-specific |
Morphologic Features
Not a cell-morphology topic. Serologic typing with anti-Le(a)/anti-Le(b) and panel identification.
Laboratory Characteristics
- Often IS/RT reactive; may clear at AHG after warm processing
- May interfere with ABO reverse typing
- Enzyme panels often enhance Lewis reactions
- Neutralization methods only if SOP-validated
Reference Intervals
Categorical phenotypes. Criteria treating Lewis antibodies as insignificant versus requiring special units are institutional, verify SOP; do not invent absolute rules.
Clinical and Laboratory Significance
Correctly recognizing Lewis antibodies as usually insignificant avoids unnecessary phenotype-matched inventory use while still requiring complete identification and ABO concordance.
Differential Considerations
Cold anti-Le(a)/Le(b) vs anti-M vs anti-I/IH vs P1 vs rouleaux, use panel antigen maps, auto-controls, and thermal techniques per SOP.
Comparison Tables
Lewis contrast map
| Feature | Lewis | Rh/Kell (contrast) |
|---|---|---|
| Antigen source | Plasma adsorption | Integral membrane protein |
| Typical Ab | Cold IgM | Warm IgG |
| Usual RBC significance | Insignificant | Significant |
| Neonatal typing | Often Le(a−b−) | Intrinsic antigens present |
Classification Frameworks
Not applicable, blood group system (ISBT LE), not a WHO disease classification.
Laboratory Notes
- Identify and document even if units need not be Lewis-negative
- Escalate atypical AHG-reactive or hemolytic Lewis patterns
- Do not apply “insignificant” label to every cold antibody
References
Authoritative textbooks, guidelines, and reviews supporting this reference entry. Verify reference intervals, critical limits, and reflex criteria against institutional protocols and current guideline editions.
Textbooks
- Cohn CS, Delaney M, Johnson ST, Katz LM, eds. Technical Manual. 21st ed. AABB; 2023.
- Harmening DM. Modern Blood Banking & Transfusion Practices. 7th ed. F.A. Davis; 2019.
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021.
CLSI and Professional Guidelines
- AABB. Standards for Blood Banks and Transfusion Services (verify current edition and institutional adoption).
- U.S. Food and Drug Administration. Code of Federal Regulations Title 21 . Blood and Blood Components (verify current institutional adoption).
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