Vox Sang. 49; 211-214 (1985) Q 1985 S. Karger AC, Basel 0042-9007/85/0493-0211 $2.75/0

Allo-anti-Pl in a Pl-Positive Person

Peter Norman“, Don MacIntyreb, Joyce Poole‘, Ma1 Mallad a Red Cross Reference Laboratory, Adelaide, South Australia, Australia; Queen Elizabeth Hospital BTS, Woodville, South Australia, Australia; ‘ WHO Blood Group Reference Laboratory, Oxford, UK;

Royal Newcastle Hospital and District BTS, New South Wales, Australia

Abstract. An allo-anti-PI antibody is reported in an elderly Caucasian male with PI+ red cells. There was no suggestion that the antibody was causing haemolysis. The case suggests that a slight structural variation may exist in the patient’s B antigen giving a serological false-positive response when typed with reagent anti-PI, or that the patient’s anti-PI is directed against a determinant absent in the patient’s own antigen structure.

Introduction

A red cell agglutinin showing PI specific- ity was detected in the serum of a man whose red cells typed as PI+. Whereas autoagglutin- ins having specificities directed against com- mon blood group antigens are being re- ported in a growing number of cases, the occurrence of non-autoagglutinins appar- ently having specificities directed against antigens present on the patient’s own cells is comparatively rare [4, 20-231. Usually this type of phenomenon is associated with anti- gens thought to be partially deficient in structure, as demonstrated by the ‘mosaic’ type of the D” antigen [3].

Case Report

The patient (Mr. B.) was admitted to hospital with pneumonia and recurrent gastro-intestinal bleeding.

Drug therapy on admission included iron, trimetho- primhlphamethoxazole and salbutamol. a-Methyl- dopa therapy had been discontinued some months pre- viously.

Following a request for compatibility testing, a weak to moderate anti-P, was detected with a negative autologous control and direct antiglobulin test, yet the patient’s red cells typed as PI+. Two units of P,- and two units of crossmatch-compatible PI+ blood were trans- fused uneventfully. The patient required no further transfusion during convalescence, but his condition deteriorated following a stroke and he died 3 months later.

Materials and Methods

All serological tests were performed using standard test tube procedures with a 1-hour incubation. The enzyme tests performed were by two-stage papain tile [ 5 ] . Reagent anti-P, sera included ‘in-house’, commer- cial and material received from the SCARF (Serum, Cells and Rare Fluids) International Exchange Pro- gram. Elution studies to recover anti-PI from P,+ cells were performed by the method of Landsteiner and Miller [6].

212 Norman/McInt yre/Poole/Mallan

Results

The patient’s cells typed as Gp B, rr, K-, Fy(a+b+), Jk(a+b+), Le(a-b+), Tj(a+), P+, MMSs, I+, Lu(a-). The patient’s red cells typed as PI+ with thirteen sources of human and goat antisera. The strength ofhis PI anti- gen expression could be described as weak to moderate against most reagent anti-PI. The direct antiglobulin test was negative. An ag- glutinin demonstrating PI specificity was de- tected in the patient’s serum, which only reacted in the cold with cells bearing mod- erately expressed or stronger PI antigens. The antibody was absorbed by both adult and cord PI+ cells, but not by adult or cord PI- cells or by the patient’s own cells. The heat eluate of adult and cord P,+ cells was neutralized by hydatid cyst fluid.

The patient’s two sons were group AB, rr, PI+. No atypical antibodies were detected in their sera; however, the cells of the one son available for further testing were aggluti- nated by the patient’s serum from which anti-A had been adsorbed.

Discussion

Following the discovery of the P blood group system by Landsteiner and Levine in 1927 [7], the system aroused little interest for another 24 years, at which time the Tja anti- gen was described [8].

The knowledge of the complexities of the system grew with the identification of the Pk antigen in 1959 [9, 101 and later an associa- tion with the ABO system was established with the discovery of the Luke serum [ll].

Further, auto-antibodies with P specific- ity have been reported [12-141. The finding of an ‘allo-antibody’ with PI specificity in a

patient whose red cells typed as PI+ may suggest further heterogeneity at the P locus. One previous case of an anti-PI in an indi- vidual whose red cells typed as PI+ has come to the authors’ attention [15]; however, this antibody appeared to be an autoagglutinin possibly causing haemolysis. The antibody reported herein was not an autoagglutinin and there was no clinical suggestion of re- duced red cell survival, the former finding being supported by a negative direct anti- globulin test and the failure of the patient’s cells to absorb and elute his own anti-PI. Comparable reactivity of the antibody with adult (IPl+) and cord (IPl-) cells suggests the specificity was not anti-IP,, previously re- ported by Issitt et al. [16].

Unfortunately, the death of the patient prevented further investigations of this ‘anomaly’ but it is interesting to speculate on a possible explanation.

Cases have been reported in the literature where, during periods of illness, patients have ‘lost’ blood group antigens and devel- oped corresponding antibody. This phe- nomenon has been demonstrated with the Kpb [18] and LW [19] blood groups. It is pos- sible that this patient similarly ‘lost’ his P I antigen during his illness, developed anti-P, and was subsequently investigated during recovery when antigen and antibody were present simultaneously. Unfortunately, re- sults of investigations suitably long enough before or after his illness were not available to confirm this theory.

Alternatively, the patient’s PI antigen may have been structurally deficient in rela- tion to the ‘normal’ antigen, and the anti- body produced was directed against the ab- sent or altered portion of the antigen. The presence of an antibody directed against the ‘absent’ structure may not be unexpected,

Allo-anti-PI in a P1-Positive Person 213

since the patient was an active pigeon breeder for many years and was presumably exposed to constant immunological stimuli [ I , 21. Whether this was the cause and whether his marked exposure to pigeon pro- tein was associated with his clinical state remains conjecture - possibly fiirther studies involving both group PI+ and P,- pigeon breeders will provide some answers.

Another possible explanation may in- volve the similarity between the B and PI antigens [17]. It appears that a conforma- tional change in the area of the immuno- dominant trisaccharide present in the anti- gens results in either B or PI specificity. Despite this close similarity, cross-reactivity has not been reported. Possibly this case may indeed represent a conformational change demonstrating cross-reactivity . The transfer of the altered antigen to the son tested against the absorbed test serum could have been masked by the presence of a normal maternally acquired antigen.

Conclusion

The discussion presented is completely speculative and further studies were pre- vented by the patient’s death. It would seem possible that further heterogeneity may exist at the P locus and that study of selected pop- ulation groups such as pigeon breeders may reveal similar cases such as this.

Acknowledgements

The authors wish to thank Dr. P. Tippett and Mr. B.M. Lyle for their constructive comments on the investigations, Dr. G. W. G. Bird and Dr. R. W. Bed for their critical review ofthe manuscript, and Miss S. Col-

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Received: December 27, 1984 Revised manuscript received February 14, 1985 Accepted: March 4, 1985

P. Norman, Red Cross Blood Transfusion Service, 301-309 Pirie Street, Adelaide, South Australia, 5000 (Australia)