An update to Kidd blood group system.

Since publication of the original Immunohematology review of the Kidd blood group system in 2015 (Hamilton JR. Kidd blood group system: a review. Immunohematology 2015;31:29-34), knowledge has mushroomed pertaining to gene structure, alleles causing variant and null phenotypes, clinical significance in renal transplant and hemolytic disease of the fetus and newborn, and physiologic functions of urea transporters in non-renal tissues. This review will detail much of this new information.

Albumin-indirect antiglobulin test.

CONCLUSIONS: Albumin was the first widely used additive solution for hemagglutination tests. Its major effect is to decrease the repulsive forces that keep red blood cells (RBCs) apart. This effect may enable some RBC antibodies, particularly those in the Rh blood group system, to directly agglutinate antigen-positive RBCs after 37°C incubation. The impact of albumin on antibody binding before detection by an indirect antiglobulin test (IAT) is minimal. Use of albumin in antibody identification may help with separation of RBC antibody specificities in a mixture when one or more antibodies demonstrate reactivity after 37°C incubation. Warm autoantibodies can show decreased reactivity in albumin IATs, allowing recognition of underlying alloantibodies.

Saline-indirect antiglobulin test.

CONCLUSIONS: A saline-indirect antiglobulin test (IAT) is performed without addition of enhancement media to increase the binding of antibody to the red blood cell antigen during the 37°C incubation. Although infrequently used as a primary means for antibody detection or identification, this test is useful because of the variety of possible applications in antibody identification studies. It is critical to the test sensitivity to allow enough incubation time (30-60 minutes) for maximum antibody binding to occur. The saline test can also be subject to a direct agglutination reading after immediate spin, room temperature, or incubation at 37°C before conversion to the IAT. This step allows further flexibility in assessing the reactivity of directly agglutinating allo- or autoantibodies in tests performed at 37°C or lower temperatures.

Kidd blood group system: a review.

The Kidd blood group system has been recognized as clinically important in red blood cell (RBC) serology since its identification in 1951. Forty years later, the JK glycoprotein was determined to be a product of SCL14A1 and was identical to the urea transport protein UT-B produced by HUT11A. The functional role of the protein as a urea transporter in RBC and kidney has been well documented. The polymorphism responsible for the antithetical anigens Jk(a) and Jk(b) was identified in 1994 as c.838G>A (p.Asp280Asn). Recent discoveries have expanded the system to include 23 variant alleles recognized by the International Society of Blood Transfusion that silence the protein expression and 7 variant alleles presumably producting weak or partia JK antigens. Null phenotypes have been identified in individuals of several populations including those of African, Indian, and Chinese decent, in addition to the well-documented findings in the Polynesian and Finnish populations. This review will examine the historical information about the anigens and antibodies of the JK system as well as catalog the variations of the JK gene.