Authors: Danielle Meunier, MD; Sophia Peng, MD; and Gwen Clarke, MD, FRCPC
Publication date: September 2019
Primary target audiences: Medical laboratory technologists (MLT) in a hospital laboratory, transfusion medicine physicians

Key points

  • Anti-Jsa is clinically significant.
  • Patients with anti-Jsa should receive Jsa-negative blood crossmatch compatible by IAT at 37°C for transfusion.
  • Patients with sickle cell disease who have anti-Jsa should be provided with Jsa-negative red blood cell units for transfusion.


Jsa (KEL6) is an antigen of the Kell blood group system. It is one of 35 Kell antigens located on the red blood cell transmembrane glycoprotein known as CD238. Some of these antigens are highly immunogenic and, after the ABO and Rh blood group systems, are the most immunogenic group for red blood cell antigen alloimmunization.

The Jsa antigen is almost exclusive to people of African origin, occurring at a rate of 20% in this population. It is very rare in Caucasians (<0.01%) and absent in people of Asian descent.

Jsa was first described in 1958 and is named after John Sutter, the first producer of the antibody. It was later assigned to the Kell system in 1965.

Anti-Jsa may occur naturally (i.e. arising without stimulus by transfusion or pregnancy-related red blood cell exposure), although this is rare; it is more likely to be an immune-stimulated IgG antibody.

Patient management: pre-transfusion and prenatal testing

In the context of transfusion, anti-Jsa is clinically significant and has been implicated in acute and delayed hemolytic transfusion reactions as well as hemolytic disease of the fetus and newborn (HDFN), which can be severe given the presence of Kell antigens on erythroid precursors. When anti-Jsa is detected in a patient’s pre-transfusion sample testing (current or historical), it is usually detected in the context of screening for other antibodies since routine screening for anti-Jsa is not performed. However, if anti-Jsa is detected, antigen-negative blood that is serologically crossmatch compatible in the 37°C IAT phase should be provided. Routine donor antigen typing (phenotyping) at Canadian Blood Services does not include Jsa typing, therefore a request for Jsa-negative red blood cell units results in additional manual phenotyping and/or genotyping.  See Table 1 for a summary of recommendations for red blood cell transfusion in patients with non-ABO antibodies.

Patients with sickle cell disease

For sickle cell disease patients without antibodies, most guidelines recommend transfusion of Rh- and Kell-matched units. For those patients with one or more antibodies (current or historical), complete donor phenotype/genotype matching is often recommended. Typically, this matching includes the Rh, Kell, Kidd and Duffy blood group systems along with the S/s antigens. If a patient with sickle cell disease develops an anti-Jsa, then Jsa-negative units should be provided, along with matching for the full extended phenotype. Given the increased risk of hyperhemolysis in patients with sickle cell disease, this clinical context necessitates full compatibility with the patient’s antigen and antibody profile.

Table 1: Red blood cell transfusion for patients with non-ABO antibodies

Patient Antibody Recommendation for red blood cell transfusion*
Diego system
Anti-Dia Red blood cell units crossmatch compatible by IAT at 37°C
Anti-Wra Red blood cell units crossmatch compatible by IAT at 37°C
Kell system
Anti-Jsa Jsa-negative red blood cell units crossmatch compatible by IAT at 37°C
Anti-Kpa Red blood cell units crossmatch compatible by IAT at 37°C
Lewis system
Anti-Lea, Anti- Leb, and Anti-Lea Red blood cell units crossmatch compatible by IAT at 37°C
Lutheran system
Anti-Lua Red blood cell units crossmatch compatible by IAT at 37°C
MNS system
Anti-M Red blood cell units crossmatch compatible by IAT or equivalent using IgG antihuman globulin
Rh system
Anti-Cw Red blood cell units crossmatch compatible by IAT at 37°C
Anti-V V-negative red blood cell units crossmatch compatible by IAT at 37°C

* Note: Patients with sickle cell disease who develop any one of the antibodies listed here should be provided with antigen-negative red blood cell units for transfusion.

Additional resources

For an introduction to immunohematology and the foundations of blood bank compatibility testing, visit, an online educational resource developed by transfusion medicine specialists in Canada. The curriculum consists of six modules and includes an interactive module for completing an antibody investigation panel.

Suggested citation

Meunier D, Peng S, Clarke G. Kell System: Anti-Jsa [Internet]. Ottawa: Canadian Blood Services; 2019 Sept 25 [cited YYYY MM DD]. Available from:


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