Transfusion medicine
Red blood cell antigens
Kidd system
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PubMed Search: Kidd blood group system
Table of Contents
Definition / general | Essential features | Terminology | Antigens | Antibodies | Pathophysiology | Clinical features | Transmission | Laboratory | Case reports | Additional references | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2Cite this page: Adkins BD, Booth GS. Kidd system. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/transfusionmedkiddsystem.html. Accessed April 2nd, 2025.
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
- Type: peptide
- 3 significant antigens: Jka, Jkb and Jk3 (AABB: Technical Manual, 20th Edition, 2020)
- Jka and Jkb are frequently expressed in most ethnic populations (AABB: Technical Manual, 20th Edition, 2020)
- Individuals negative for both antigens Jk(a-b-) are infrequent except in Polynesian and Finnish populations but can form antibodies against Jk3, a high incidence antigen in all individuals with any Jk positivity (Transfus Med Rev 2017;31:165)
- Kidd glycoprotein is encoded by the HUT11 / UT-B / JK (SLC14A1) gene encoded at 18q12-q21 (Transfus Med Rev 2017;31:165)
- Kidd glycopeptide functions as a transmembrane urea transporter on red cells, which helps to maintain cellular osmotic stability; also helps the kidney concentrate urine (AABB: Technical Manual, 20th Edition, 2020)
| Jk(a+b-) | Jk(a+b+) | Jk(a-b+) | Jk(a-b-) | |
| White | ||||
| Black (U.S.) | ||||
| Asian |
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 IgG3, which are better at fixing complement; this causes intravascular hemolysis clinically (Klein: Mollison's Blood Transfusion in Clinical Medicine, 12th Edition, 2014)
- 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
- Newborn girl with hemolytic disease caused by anti-Jkb antibodies (Indian J Hematol Blood Transfus 2014;30:135)
- 32 year old woman with sickle cell disease developed hyperhemolysis secondary to multiple antibodies including Jkb (Indian J Hematol Blood Transfus 2016;32:251)
- 73 year old man with Jk3 sensitization after cardiac surgery (Kyobu Geka 2017;70:457)
- Case series of Jk3 antibody positive mothers (Transfusion 2018;58:1157)
- Novel Jk allele associated with Jk3 antibody production (Transfusion 2018;58:1078)
Additional references
Board review style question #1
A patient has a negative antibody screen and receives a red blood cell (RBC) 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?
- Dosage
- Dithiothreitol treated red cells
- Enzyme treated red cells
- Evanescence
Board review style answer #1
D. Evanescence. Evanescence refers to the nature of antibody levels going below the level of detection but rising due to the body’s anamnestic response. This is due to long lived plasma cells residing in the bone marrow, which produce antibodies against red cell antigens. Answer A is incorrect as dosage refers to the zygosity of certain RBC antigen genes and the resultant reactivity with laboratory antisera. Answers B and C are incorrect because they refer to different immunohematology techniques that can help characterize antibodies' reactivity against certain antigens.
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Reference: Kidd system
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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?
- 1M / 2M
- 2M / 2M
- 2M / 5M
- 5M / 5M
Board review style answer #2
C. 2M / 5M. 2M urea is classically used to test the urea transport ability of red blood cells (RBC); cells that lack the Kidd urea transporter proteins will resist lysis in this concentration. Conversely, 5M urea is used to test for the presence of crosslinking in fibrin clots, with increased solubility being indicative of factor XIII deficiency. Answers A, B, and D are incorrect because these other concentrations are not classically used for these tests.
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Reference: Kidd syste
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