Global Journal of Transfusion Medicine

: 2020  |  Volume : 5  |  Issue : 2  |  Page : 218--220

A report of rare p phenotype and anti-PP1Pk antibody from North India

Saini Nishant1, Sachdeva Puneet2,  
1 Department of Transfusion Medicine, Patel Hospital, Jalandhar, Punjab, India
2 Department of Transfusion Medicine, Paras Hospitals, Panchkula, Haryana, India

Correspondence Address:
Sachdeva Puneet
Department of Transfusion Medicine, Paras Hospitals, Panchkula, Haryana


A requisition for one unit of packed red blood cells (PRBCs) was received for a patient of carcinoma oral cavity admitted in our hospital. Blood group discrepancy was encountered while performing routine serological investigations on the patient's blood sample. Random cross-match with multiple ABO-identical and ABO-compatible PRBC units was found to be incompatible. Further immunohematological workup was performed which led to the discovery of the patient having rare p phenotype.

How to cite this article:
Nishant S, Puneet S. A report of rare p phenotype and anti-PP1Pk antibody from North India.Glob J Transfus Med 2020;5:218-220

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Nishant S, Puneet S. A report of rare p phenotype and anti-PP1Pk antibody from North India. Glob J Transfus Med [serial online] 2020 [cited 2021 Jul 26 ];5:218-220
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While performing routine serological testing on patient's blood sample, occasionally, we may encounter ABO blood group discrepancy and/or ABO-incompatible cross-match. It can be a challenging situation to find compatible blood in a timely manner, in case it is associated with pan-reactive red cell antibody screening and identification (ID) panel. One of the causes of pan-reactive ID panel is antibody against high prevalence red cell antigen, owing to the absence of that antigen on the patient's red cells.[1] To find compatible blood in such a situation can be extremely difficult due to restricted resources available for an advanced serological workup, especially in developing countries like India. We report here the first case from North India ofp phenotype with anti-PP1Pk antibody.

 Case Report

A requisition for packed red blood cells (PRBCs) transfusion was received for a male patient aged 39 years diagnosed with carcinoma oral cavity. He had been operated a few months back and was now scheduled to receive chemotherapy and radiation therapy. His hemoglobin was 6.6 g/dl. He was hemodynamically unstable and admitted under the intensive care unit. There was no history of any previous transfusion or transplantation. No other alloimmunizing episode could be identified.

The requisition was processed as per the standard operating procedure (SOP) of our blood bank. As a part of preliminary workup, patient's blood grouping was performed, the results of which are given in [Table 1].{Table 1}

As there was an ABO blood group discrepancy, further serological workup was performed by column agglutination technology (CAT), the results of which are given in [Table 2].{Table 2}

On the basis of history and above-mentioned serological workup, initial interpretation of a naturally occurring antibody/alloantibody against a high prevalence red cell antigen was made.

As the transfusion was urgent, to find compatible blood, random cross-matching with about 40 A-positive, A-negative, O-positive, and O-negative packed red cell units was performed. All the blood bags were found to be incompatible (3+ to 4+) by both CAT and test tube method. No first-degree family member was available for sampling and cross-matching since the patient's only sibling was ABO incompatible (AB positive) and both his parents had expired. Cross-match was performed with samples collected from ABO-identical and ABO-compatible other relatives which also showed 3+ to 4+ incompatible reaction. The physician was informed about the inability to arrange compatible blood. As the patient needed urgent transfusion, transfusion with O neg PRBC unit which was also incompatible with patient's sample was given. After taking consent from the patient and his physician, red cell transfusion was started under high-dose steroid cover and close observation. Unfortunately, after initial few milliliters of red cell transfusion, the patient started complaining of uneasiness and developed flank pain, suggestive of acute hemolytic transfusion reaction. Transfusion was stopped immediately. The patient was stabilized. Adverse transfusion reaction workup was performed which showed findings similar to that of pretransfusion testing. Direct antiglobulin test on posttransfusion reaction sample was negative. Few days later, he was given a trial of erythropoietin which raised his hemoglobin. No further requisition for transfusion was received as the patient became hemodynamically stable.

For further workup, samples were sent to the International Blood Group Reference Laboratory (IGBRL), Bristol, UK, where serological and genetic workup was done. It was found that the patient has the rarep phenotype (P-, P1-, Pk-) with anti-PP1Pk antibody present in the plasma. The anti-PP1Pk antibody reacted strongly by low ionic strength solution (LISS) indirect antiglobulin test (IAT) and showed direct agglutination with untreated and papain-treated cells at 37°C and also reacted weakly at 18°C showing direct agglutination. The findings were further confirmed by cross-matching fourp samples with the patient's plasma and found compatible. No additional antibodies were detected. Further DNA analysis of the exon 2a and exon 3 of A4GALT gene which encodes the antigens of the P1Pk blood group system was performed. Sequencing of exon 2a revealed the patient to be homozygous for 42C and 122T, associated with the P1 phenotype. Sequencing of exon 3 revealed homozygosity for a missense mutation, 109A>G (p. Met37Val) and a 2 base-pair deletion, del547_548AT, resulting in a frame-shift (p. Met183Valfs*99). These mutations are similar to those carried by the known null allele, A4GALT*02N.07, although the previously reported allele also carries a further missense mutation, 367T>C, which is not present in this patient. However, as the observed 2 base-pair deletion causes a reading frame-shift, homozygosity for this allele is still predicted to result in a null, pp phenotype.


Earlier, thePblood group system comprised the P, P1, and Pk antigens, and later, Luke (LKE) was added to it. Currently, in ISBT nomenclature, P1 and Pk are assigned to P1Pk blood group system (003) which also has another antigen called NOR, whereasPis assigned to the Globoside blood group system (028) and LKE and PX2 to the Globoside collection (209) owing to the location of genes involved in the development and expression of these antigens at different loci. The antigens were renamed as P1 (denotes P+) and P2 (denotes P−) based on the presence or absence ofP antigen, respectively.[2] Pk antigen is usually detected whenP antigen is absent.[3] Based on the different combinations of these antigens, two common phenotypes P1 and P2 and three rare phenotypes p, P1k, and P2k are described wherep denotes absence of all three antigens, i.e., P, P1, and Pk. Individuals with thep phenotype (sometimes calledP null) are very rare about 5.8 in a million. They are more common in Japan, North Sweden, and in an Amish group in Ohio.[4]

Two genes are involved in the synthesis ofPblood group system antigens. One named A4GALT encodes for an enzyme α1,4-galactosyltransferase, which causes the synthesis of Pk antigen. Pk antigen then serves as a substrate for another enzyme β1,3-N-acetylgalactosaminyltransferase encoded by another B3GALNT1 gene to form theP antigen. Several inactivating mutations have been found in both A4GALT and B3GALNT1 genes. Thep phenotype not only is the consequence of mutations in the protein-coding sequence of A4GALT but can also be the result of deletions in noncoding upstream exons. Similar findings were seen in our case also where a 2 base-pair deletion resulting in a reading frame-shift caused the development of null, pp phenotype. In the absence of A4GALT- encoded activity, there is a loss of all globo-family and P1 antigens. Mutations in B3GALNT1 give rise to Pk phenotype, which is characterized by a loss of P, LKE, and PX2 antigens and by increased Pk expression.[3],[5]

Anti-PP1Pk antibody was originally described by Levine et al. in 1951 in appatient with adenocarcinoma of the stomach and was called anti Tja.[6]Psystem antigens were present on her tumor cells, and the antibody was credited to have cytotoxic properties. It is not present at birth in the serum ofp infants but develops early in life without exposure to foreign red cells.[7] It reacts with all RBCs except those of thep phenotype which was confirmed in our case also.

The anti-P, anti-P1, and anti-Pk components of anti-PP1Pk are separable through adsorption.[8] Both IgM and IgG components can be present, and they can react over a wide thermal range as was also evident in our case. We also found that the anti-PP1Pk antibody reacted strongly by LISS IAT at 37°C and also reacted weakly by direct agglutination at 18°C. It can efficiently bind and activate complement which makes it a potent hemolysin. As a result, the antibody has the potential to cause severe Hemolytic transfusion reactions (HTRs) and Hemolytic disease of fetus and newborn (HDFN).[6],[9] In our case also, a trial of incompatible red cell transfusion was given. Within few minutes of transfusion, patient started complaining of signs/symptoms suggestive of acute hemolytic transfusion reaction. Similar findings were reported by Levine et al.[6] In the patient in whom the antibody was found, a test injection of 25 ml of incompatible blood was followed by an immediate severe reaction with hemoglobinemia. Subsequently, the antibody titer rose from 8 to 512. The antibody is also associated with an increased incidence of spontaneous abortion in early pregnancy probably, due to an IgG anti-P component.[10]

To conclude, we would like to recommend that an advanced level immunohematology reference laboratory is needed in India along with a rare blood donor program to detect rare phenotypes which are known to be associated with HTR and HDFN. Establishing a rare donor registry can help in creating a pool of donors who can be contacted in times of emergency.[11] This would help in providing timely transfusion support in case of transfusion requirement by such patients. Although this can prove a major step toward better transfusion services, resource constraints would pose a hindrance. Many more cases might have been missed due to the lack of advanced immunohematology facilities in our country. Recently, first report ofP null phenotype from India has been published.[12] The clinical and serological findings in this report were similar to those in our case, except that the mutation at the genetic level was different. Still, ours is the first case report ofp phenotype from North India.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. The patient understand that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.


This case was worked up and solved with the help of IGBRL, Bristol, UK.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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