ANOTHER CASE OF PARA-BOMBAY PHENOTYPE IN

AN IRANIAN DONOR

 

Abbasali Pourazar PhD^•*, Sanmukh Joshi PhD**, Vander A. Clarke MD***,

Fereidoon Ala MD***

 

 

The blood specimen of a 42-year-old male donor was targeted for detailed study at the Iranian National Blood Transfusion Services as the ABO blood grouping of his cells and serum did not match. Preliminary results suggested that his group was “Bombay” (Oh) phenotype. For confirmation, his blood specimen was air-shipped to Bombay, where detailed studies revealed the presence of depressed A antigens on his red cells that were detectable with variable strength with anti-A+B reagents prepared from group O individuals. His red cells failed to show agglutination by anti-H reagents from “Bombay” phenotype, lectin from Ulex europaeus, and immunized chicken. The donor’s serum agglutinated group B red cells showing a titer of up to 1:32 at room temperature, but reacted with A and O red cells only at 4˚C in a low titer of 1:4 – 8. The reactivity against group A and O cells was partially inhibited by saliva from individuals secreting A/H antigens and was characterized as anti-I. The donor was classified as para-Bombay of AHw phenotype. The anti-I antigen strength on the donor’s red cells, as determined by titration of anti-I and anti-i reagents, was comparable to normal adult individuals but not to the “Bombay” phenotype, thus supporting his phenotype as para-Bombay. This case provides another example of the para-Bombay phenotype that serologically differs from the one reported earlier in Iran. 

 

Archives of Iranian Medicine, Volume 7, Number 4, 2004: 284 – 286.

 

Keywords: I-i antigen · para-Bombay

 

Introduction

 

ombay” and “para-Bombay” phenotypes are rare blood types, the former being more common than the later in the Indian subcontinent.¹ The Bombay phenotype differs from the para-Bombay phenotype with respect to their ABH and I-i blood groups’ profile. Bombay phenotype individuals lack ABH antigens on red cells and possess corresponding alloantibodies in serum,² the antibodies reacting with equal strength at 4˚C as at 37˚C.^{3, 4} In contrast, the red cells of the para-Bombay phenotype react weakly, depending on the presence of the ABO gene, with antisera to ABH antigens.  The  weak  reaction  has  to  do  with  the presence of the ABO genes. These antibodies moderately react with ABO system antigens.  Another difference in the para-Bombay phenotype is that atypical antibodies in the serum react preferentially at lower temperatures (below 20 – 22˚C). Having the special characteristics of anti-I in secretors and anti-H in nonsecretors make this phenotype more special.  Additionally, red cells of the Bombay phenotype⁵ show an increased strength of the I-i antigen,^{4, 6} whereas those of the para-Bombay phenotype exhibit a normal I-i antigen profile.¹ We describe here a case of para-Bombay phenotype in an Iranian blood donor that serologically differs from the earlier reported case of para-Bombay from the region.⁷

 

Materials and Methods

 

Antisera to ABO blood groups used in the study were prepared and standardized locally or were from commercial sources. Anti-H reagents were from locally detected cases of Bombay phenotype, immunized chicken, and lectin extracted from the seeds of Ulex europaeus anti-I (Steph) and anti-i (Ziag) from P Issitt, USA. The blood specimens of the donor, collected in plain and EDTA-containing vials were transported by air on ice. Adult and cord blood samples, used as controls, were taken respectively from the blood banks of KEM Hospital and Wadia Maternity Hospital, Bombay, India. The methods used throughout were the standard serological procedures recommended by Bhatia.⁸

 

Results

 

 

 

 

Donor 552 was a 42-year-old male blood donor identified at the Iranian National Blood Transfusion Services for detailed investigations into a discrepancy in ABO blood grouping. Preliminary grouping on his blood showed forward cell group as O, while reverse serum group showed reactivity against all A, B, and O screening cells with somewhat weaker agglutination pattern with groups A and O red cells. As the donor’s red cells failed to react with anti-H lectin, it was suspected that he could have a blood group abnormality such as Bombay (Oh) phenotype. The donor’s blood was sent to Bombay for confirmation. Observations made in Iran were reproduced in Bombay, as his red cells failed to show direct agglutination with the batteries of anti-A, anti-B, and anti-H (Oh) (8 batches of each) anti-H (chicken), and anti-H (Ulex europaeus lectin). Interestingly, 6 out of 8 anti-A+B reagents, from group O subjects, showed agglutination of the donor’s red cells with variable strength. An absorption-elution experiment showed that the donor’s red cells, sensitized with anti-A, anti-A+B, and anti-H (human and chicken) gave active eluates that were inhibited by appropriate secretor saliva (Table 1), thus confirming the presence of weak A and H antigens on his red cells. Surprisingly, no reactivity was eluted from the donor’s cells sensitized by anti-H (Ulex europaeus). Investigations into the donor’s serum showed a titer of 1:16 – 32 against group B red cells at room temperature and at 4˚C. This antibody was identified as anti-B. On the other hand, his serum agglutinated group A and O red cells in a low titer of 1:4 – 8 only at 4˚C. The reactivity with group A and O red cells was partially inhibited by saliva from group A and O secretors and reactivity was weaker with cord red cells than those of an adult, thus indicating its specificity as anti-I (Table 2).

Table 3 shows the I-i antigen strength of the donor’s red cells as compared to the adult and cord blood samples. The donor’s cells showed a titer of 1:32 with anti-I that was comparable to the normal adult level. The anti-i, not reacting with the adult red cells, reacted weakly with the donor’s red cells thus suggesting its normal adult level (Table 3).

 

 

Discussion

 

The Bombay phenotype is characterized by group O which lacks H antigen on red cells and by the presence of anti-H along with anti-A and anti-B in the serum.² The para-Bombay phenotype, on the other hand, possesses weakly expressed ABH antigens on the cells, depending upon the presence of corresponding genes.⁴ The weak antigen in para-Bombay phenotype can be appreciated by virtue of the cells giving weak reactions with anti-A, anti-B, or anti-H and by successful elutions of antibodies in accordance with the suppressed antigens.⁴ The red cells of  donor 552 were not agglutinated by anti-A and anti-H and showed direct agglutination with anti-A+B reagents, however, weaker forms of A and H antigens were revealed by the antibodies eluted from the sensitized red cells by not only anti-A+B but also by anti-A and anti-H reagents. These observations support a diagnosis of para-Bombay phenotype in this donor.

Antibodies in the serum of Bombay phenotype show no variations in titer at different temperatures, even in cases with known suppression of A or B antigens.^{3, 4} On the other hand, individuals with para-Bombay phenotype may possess antibodies preferentially reacting at lower temperatures with a serological specificity such as anti-I or anti-H, depending upon the presence or absence of the secretor gene in an individual.¹ In the present case, the antibody reactivity against group A and O red cells was found only at 4˚C and with anti-I specificity.  This further supports the conclusion that the donor belongs to the para-Bombay phenotype category, although we have not tested the donor for his secretor status. 

The para-Bombay phenotype also differs from the Bombay phenotype due to a difference in the types of red cell I-i antigens. The para-Bombay phenotype possesses normal adult levels of the I-i antigens,¹ whereas the Bombay phenotype may possess elevated levels of these antigens.^{1, 4, 6} The titer values of anti-I and anti-i obtained against the donor’s cells were similar to those found in normal adult individuals, further suggesting that donor 552 belongs to the para-Bombay phenotype. The present case of the para-Bombay phenotype differs from the earlier reported case⁷; the present case shows direct agglutination with Anti-A+B reagents from group O persons and there are differences between the present and former case with respect to I-i blood group profile. The phenotype reported earlier⁸ showed depressed I and elevated I antigen whereas the present case shows a normal expression of the I-i antigens.

 

 References

 

1     Bhatia HM, Sathe M, Joshi SR. Incidence, serology, and genetics of “Bombay” (Oh) and “para-Bombay” phenotypes. Proc Recent Trends in Immunohaematol. 1982: 1 – 9.

2    Bhende YM, Deshpande CK, Bhatia HM, et al. A "new" blood group character related to the ABO system. Lancet. 1951; 1: 903 – 904.

3    Moores PP. Blood Groups of the Natal Indian People [PhD thesis]. Durban, South Africa: Natal University; 1980.

4    Bhatia HM. Serologic reactions of ABO and Oh (Bombay) phenotypes due to variations in H antigens. In: Mohn JF, Plunkett RN, Cunningham RK, Lambert RM, eds. Human Blood Groups. 1st ed Basel: Karger; 1977: 296.

5     Race RR, Sanger R. Blood Groups in Man. 6th ed.  Oxford: Blackwell; 1975.

6    Moores PP, Issitt PD, Pavone BG, McKeever BG.  Some observations on "Bombay" bloods, with comments on evidence for the existence of two different Oh phenotypes. Transfusion. 1975; 15: 237 – 243.

7    Joshi SR, Pourazar A, Clarke VA, Ala FA. Para-Bombay phenotype with altered I-i blood group antigens in an Iranian donor. Transfusion Today. 2000: 3 – 6.

8    Bhatia HM. Procedures in Blood Banking and Immunohaematology. Bombay: Blood Group Reference Center, ICMR; 1977.

---

 AIM Home | Table of Contents