Transfusion medicine

Red blood cell antigens

Kidd system


Editorial Board Member: Kyle Annen, D.O.
Deputy Editor-in-Chief: Patricia Tsang, M.D., M.B.A.
Brian D. Adkins, M.D.
Garrett S. Booth, M.D., M.S.

Last author update: 13 January 2022
Last staff update: 13 January 2022

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PubMed Search: Transfusion medicine Kidd system

Brian D. Adkins, M.D.
Garrett S. Booth, M.D., M.S.
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Cite this page: Adkins BD, Booth GS. Kidd system. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/transfusionmedkiddsystem.html. Accessed February 8th, 2023.
Definition / general
  • Antigenic
  • Antibodies clinically significant
Essential features
  • Most Kidd antigens are widely expressed in the donor population
  • Antibodies can cause hemolysis and hemolytic disease of the fetus and newborn (HDFN)
  • Kidd antibodies often drop below the level of detection and are commonly implicated in delayed hemolytic transfusion reactions
  • Kidd antibodies are often capable of activating complement and can cause intravascular hemolysis
Terminology
  • Kidd a or Jka
  • Kidd b or Jkb
Antigens

Race / ethnicity
Jk(a+b-) Jk(a+b+) Jk(a-b+) Jk(a-b-)
White
26
50
24
Rare
Black (U.S.)
52
40
8
Rare
Asian
23
50
27
Rare
Adapted from AABB: Technical Manual, 20th Edition, 2020
Antibodies
  • Majority IgG, fewer IgM (AABB: Technical Manual, 20th Edition, 2020)
  • Occur with exposure to products containing incompatible blood or pregnancy
  • Antibodies tend to decrease over time; may become undetectable by blood bank methodology, posing a risk of transfusion reaction
  • Can cause hemolytic reactions and hemolytic disease of the fetus and newborn
  • Majority IgG1 or IgG3 and can fix complement (AABB: Technical Manual, 20th Edition, 2020)
  • Antibodies are enhanced when using enzyme treated red cells
Pathophysiology
  • Antibodies tend to decrease in level over time and then rapidly increase with subsequent exposure
    • Plasma cell memory is called an anamnestic response
    • Decrease in antibody level over time to a potentially undetectable level is known as evanescence
  • Antibodies formed tend to be IgG1 or IgG2, which are better at fixing complement; this causes intravascular hemolysis clinically
  • Reference: AABB: Technical Manual, 20th Edition, 2020
Clinical features
  • Kidd antibodies often drop below the level of detection and are commonly implicated in delayed hemolytic transfusion reactions
  • Kidd antibodies are often capable of activating complement and can cause intravascular hemolysis
  • Reference: AABB: Technical Manual, 20th Edition, 2020
Transmission
  • Exposure to Kidd antigens secondary to pregnancy or transfusion
Laboratory
  • 2M urea testing can be used to distinguish Kidd positive versus Kidd null individuals; Kidd positive cells will lyse with a rapid influx of urea while Kidd null cells will remain intact
  • Conversely, 5M urea is the concentration used for determining factor XIII deficiency
  • Resistant to proteolytic enzymes, such as papain and ficin
  • Reference: AABB: Technical Manual, 20th Edition, 2020
Case reports
Board review style question #1
A patient has a negative antibody screen and receives a red blood cell transfusion for symptomatic anemia. 2 days later, the patient develops hematuria and is found to have a positive direct antiglobulin test (DAT [IgG and C3]). A screen demonstrates a previously unidentified Jkb antibody. What antibody characteristic likely contributed to this delayed hemolytic transfusion reaction?

  1. Dosage
  2. Dithiothreitol treated red cells
  3. Enzyme treated red cells
  4. Evanescence
Board review style answer #1
D. Evanescence

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Reference: Kidd system
Board review style question #2
What molarity of urea is used to determine if individuals are Jk(a-b-) and to evaluate for factor XIII deficiency, respectively?

  1. 1M / 2M
  2. 2M / 2M
  3. 2M / 5M
  4. 5M / 5M
Board review style answer #2
C. 2M / 5M

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Reference: Kidd system
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