Kell system: anti-Jsa

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

Background

Js^a (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 Js^a 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.

Js^a 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-Js^a 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-Js^a 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-Js^a 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-Js^a is not performed. However, if anti-Js^a 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 Js^a typing, therefore a request for Js^a-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-Js^a, then Js^a-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.

* 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 LearnSerology.ca, 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-Js^a [Internet]. Ottawa: Canadian Blood Services; 2019 Sept 25 [cited YYYY MM DD]. Available from: https://profedu.blood.ca/en/transfusion/best-practices/serological-best-practices

Resources 

1. Storry JR. Chapter 14: Other blood group systems and antigens; The Kell and Kx systems. In: Fung M, Grossman B, Hillyer C, Westhoff C, editors. Technical Manual, 18th Ed. Bethesda: AABB; 2014. p. 345-8.
2. Reid M, Lomas Francis C and Olsson M. The Blood Group Antigens Facts Book, 3rd ed. San Diego: Elsevier Science & Technology; 2012. Section II: The blood group systems and antigens; Kell Blood Group System. p. 297-346.
3. Daniels G. Human Blood Groups, 3rd ed. Oxford: Wiley-Blackwell; 2013. Chapter 7, Kell and Kx Blood Group Systems, 7.5: Js^a and Js^b. p. 286-7.
4. NHS Blood and Transplant. NHSBT: Specification SPN214/3: The Clinical Significance of Blood Group Alloantibodies and the Supply of Blood for Transfusion. Available from: https://nhsbtdbe.blob.core.windows.net/umbraco-assets-corp/14863/spn2144-the-clinical-significance-of-blood-group-alloantibodies-and-the-supply-of-blood-for-transfusion.pdf
5. Davis BA, Allard S, Qureshi A, et al. Guidelines on red cell transfusion in sickle cell disease. Part I: principles and laboratory aspects. Br J Haematol. 2016;176(2):145-330. Available from: http://www.b-s-h.org.uk/guidelines/guidelines/red-cell-transfusion-in-sickle-cell-disease-part-l/
6. The Canadian Haemoglobinopathy Association. Transfusion. In: Consensus Statement on the Care of Patients with Sickle Cell disease in Canada. Version 2.0. Ottawa; 2018. p. 12-20. Available from: https://www.canhaem.org/wp-content/uploads/2018/05/Sickle-Cell-Consensus.pdf
7. Ito K, Mukumoto Y, and Konishi H. An example of a “naturally occurring” anti-Js^a (K6) in a Japanese Female. Vox Sanguinis. 1979;37(6):350-1.
8. Nikolis NM, Boctor F, Heaton WA, and Martone J. Should we be screening for anti-Js^a? Immunohaem. 2001;27(3):104-6. Available from: https://www.redcrossblood.org/content/dam/redcrossblood/immunohematology-journal/27_3_11.pdf