Further evidence for naturally occurring anti Jk^a antibodies

Sir,

Antibodies to red cell antigens are considered naturally occurring when there is no obvious source stimulus such as blood transfusion, injection or pregnancy. However, these antibodies are produced as an immune response to some unknown environmental antigens such as pollen grains and other parts of bacterial membranes.[1] The commonly mentioned naturally occurring antibodies belong to the ABO, Hh, Ii, Lewis, MN, P blood group systems. Anti-Kidd antibodies are notorious for confounding features and as a causal for delayed hemolytic transfusion reactions. Even strong Anti-Kidd antibodies may become undetectable after few weeks or months of immune stimulus and are frequently known to show dosage effect. Anti-Kidd antibodies are often difficult to detect and usually are commonly found in combination with other antibodies reflecting the low immunogenicity of the Kidd antigen.[2] There are numerous reports of these antibodies. Anti Jk^b is rarer than anti Jk^a and there are only two reported cases of naturally occurring anti-Kidd antibodies in the literature.[3,4] The present case confirms the possibility of naturally occurring anti-Kidd antibodies.

On routine donor antibody screening, we found a donor sample reacting with ID DiaCell Pool using column agglutination technique (BIO-RAD, DiaMed GmbH; Switzerland). As per our departmental standard operating procedure, since the initial screening test was positive we proceeded with the antibody screening with the 3 cell panel and identification with the 11 cell ID Dia Panel (BIO-RAD, DiaMed GmbH; Switzerland). Anti Jk^a antibodies were identified in the donor's sera and a dosage effect was observed. Enhancement of the reaction was observed on testing the plasma of the donor with the Jk^a positive cell panels in the presence of enzyme (BIO-RAD, ID-Papain, DiaMed GmbH Switzerland). On phenotyping the red cells of the donor by indirect anti-globulin test (IAT) method using gel card, they were found to be Jk (a−b+). Phenotyping was confirmed by adsorption elution technique. IAT was negative by tube technique. Direct anti-globulin test and auto control were negative by both tube and gel technique. Antibody titer by gel technique was 8 and after Dithiothreitol (DTT) treatment it reduced to 2. Since the IAT by tube technique was negative, titration by tube was not performed. Blood group of the patient was A Rh D negative and there was no discrepancy noted while blood grouping. All immunohematological tests were performed according to the manufacturer's instructions. Donor (38 year, male) questionnaire form was reviewed and the donor was contacted for relevant past history. No history of any surgery or invasive procedures in the past or any blood transfusion was revealed. There was no history of any major illness or infections in the recent past and was not on any medications. Similar to the case reported by Kim et al., antibody was detected by gel technique but not by tube technique.[4] However unlike their report, the decrease in titer of the antibodies after DTT treatment of the serum was observed indicating the presence of both the IgM and IgG type of antibodies. Though commercially available poly-specific or mono-specific anti-human globulin contains little activity against IgM heavy chains, it may contain anti-light chain specificity and therefore react with the cells sensitized with IgM and IgA type of antibodies as well.[5] Donor was informed about the presence of antibodies and advice for future transfusions was given.

In developing countries like India, in most of the blood banks the donor antibody screening is done by tube technique. Since there are both IgM and IgG type of antibodies in this particular case, it can bind to complement and can lead to intravascular lysis and rapid clearance of red cells especially if such fresh frozen plasma units are transfused to Jk^a positive neonates or pediatric patients.

The present report proves the importance of using more sensitive techniques for donor antibody screening. With three successive reports, anti Jk^a should be added to the list of naturally occurring antibodies.