of Acquired Tolerance to the A Antigen 417

enfants 6taient tous deux du groupe 0. Six mois aprbs le second accouchement le m&me 6tat qu’en 1953 se r6tablit.

Zusammenfassung

Die 1953 beschriebene menschliche Chimare, welche Erythrozyten der Gruppen 0 und A, aufweist, wobei die letzteren von dem vor 25 Jahren verstorbenen Zwillingsbruder stammen, wurde in den Jahren 1954155 wahrend zwei Schwangerschaften eingehend serologisch untersucht. Vor den Schwangerschaften enthielt ihr Serum A-Blut- gruppensubstanz und Isoagglutinine Anti-B. Wahrend den Schwan- gerschaften verschwand die A-Substanz, und es traten zudem Iso- agglutinine Anti-A in Erscheinung. Beide Kinder hatten die Blut- gruppe 0. Sechs Monate nach der letzten Schwangerschaft war der Zustand von 1953 wieder erreicht.

Reference

Dunsford, I . , C . C . Bowley, Ann M . Hutchison, Joan S . Thompson, Ruth Sanger and R. R. Race: A Human Blood Group Chimera. Brit. med. J. 1953/ii, 81.

Authors’ address : Drs. I. Dunsford and S. &I. Scacey, National Blood Transfusion Service, Northfield Road, Shefjeld 10 (England).

Farr. A . D.: Vux Sunguinia 2: 417-421 (1957)

A Survey of the Incidence of High-Titre Anti-A and Anti-B Agglutinins in Blood Donors in the

South- West of England

A. D. FARR

South-West Regional Transfusion Centre Southmead, Bristol

Laboratories carrying out routine grouping of donor bloods gener- ally perform a screening test for donors whose serum contains high- titre anti-A and anti-B agglutinins. In view of the fact that in this country such donors are the source of practically all the ABO group- ing serum in general use, it is a cause of surprise that very few figures appear t o have been published previously regarding the percentage

418 F a r r , A Survey of the Incidence of High-Titre Anti-A and

of donors in each group who posess an agglutinin titre sufficiently high t o render their serum of value for diagnostic purposes, Only two reports appear to have been made so far - that of Rainsford and Morgan 4, which reports on investigations on Royal Navy personnel, and that of Rangrens who examined Swedish blood donors. The figures included in this survey are taken from high-titre screening tests performed at this laboratory during a period of twenty-two months during 1954 to 1956 on some 5000 donors.

Methods (a) Selection of donors. Donors tested were D-positive persons attending civilian

sessions for the first time. The choice of D-positive donors only was made owing to the demand for D-negative blood for therapeutic purposes excluding the possibility of bleeding such donors in to dry bottles for serum. As there is no genetical asso- ciation between the ABO and Rh systems, and the few reports of serological inter- action have all been concerned with Rh immunization it is most unlikely that the selection of Rh positive donors in the present series bas influenced the results appre- ciably. The exclusion of donors a t service sessions (due to the impermanence of their postings making further bleeding of any individual unlikely) also restricted the survey to residents of the counties of Cornwall, Devon, Somerset, Gloucestershire and the western part of Wiltshire. As only donors attending for the first time were included specific selection of any donors previously tested was avoided.

(b) Screening test. The surface fixation method of screening high-titre donors introduced by Farr and Godwin* was employed. Using this method sera giving + + + and + + + + readings (approximately equivalent to titres of 1 : 32 and 1 : 64) were selected as of possible high-titre. Full titrationsperformcd on the serum of these donors when next bled (into dry bottles without anticoagulant) confirmed that practically all were in fact of suitably high titre.

(c) Period of the srirvey. The figures quoted are for the period 19th July, 1954 to 30th April, 1956, inclusive.

Results

Out of a total of 4992 donors tested, comprising 4161 Group A persons and 831 Group B, 297, i.e., approximately 6% had sera designated as of possible high titre. The distribution of these be- ween the groups was, however, significantly uneven. 161 (4%) of all Group A's were of possible high titre, as against 136 (16%) of Group B's. The figures are summarised in Table I, the percentages quoted beingto the nearest 1 %.

Of some considerable interest is the fact that when reduced t o absolute figures the balance of distribution becomes almost equal.

An analysis of 20,000 new donors in the South-West Region (McCrudden, 1956)s gives a frequency for Group A of 43.5% and Group B 8.5%. Relating these figures to those in Table I it is seen

Anti-B Agglutinins in Blood Donors in the South-West of England

TABLE I

419

Group No.high %high titre titre Tested

~ ~~~

A 4161 161 4 B 831 136 16

Total 4992 297 20

TABLE I1 ~-

% % Absolute yo Distribution High titre High titre Group

A 43.5 4 1.74 B 8.5 16 1.36

that the absolute figures are Group A 1.740% and Group B 1.360%. This is summarised in Table 11.

The effect of this is that an evenly balanced supply of both types of grouping serum is generally available.

Discussion

The uneven distribution of high-titre agglutinins amongst Group A and Group B donors is difficult to explain adequately, particularly in view of the fact that the absolute figures are almost equal. Both Rainsford and Morgan and Ramgren showed very similar per- centages. The results of these workers are summarised in Table 3, for the purposes of which the percentage distribution of Groups A and B are those (a) reported by Rainsford and Morgan for Royal Navy personnel and (b) the figures for Swedes in Stockholm quoted by Boyd l .

The fact that the actual figures for high-titre donors are lower than in the present series is doubtless due to the standard set for a mini- mum "high" titre. Whereas the present series was based on the minimum titre of 1 : 64 accepted by the Blood Group Reference Labo- ratory as suitable for inclusion in pools of high-titre sera, Rainsford and Morgan required a titre of 1 : 256 and Ramgren of 1 : 128, with A, cells, for anti-A and 1:256 for anti-B. It will, however, be seen that the approximate equality of the absolute figures is still appar- ent. Some differences may appear in other racial groups, and such figures would be of considerable interest; especially from countries

420 Farr, A Survey of the Incidence of High-Titre Anti-A and

TABLE 111

% Number % % Distribution tested High titre High titre

0.63

B 8.53 'I 7.0 0.60

1.15

I 1.5

I 2s

a. British A 42.07 (R.N.) 4.032

b. Swedes A 46.1 (Stockholm) 2.037

B 9.5 'I 10.0 0.95

where the A/B ration is reversed. The fact that the absolute figures are well balanced is particularly fortunate when considering the supply of diagnostic grouping sera.

The size of the present sample (1000 more than either of the previ- ously reported ones) is probably sufficient t o obtain a reliable average set of figures. Although no exact figures are available for earlier periods, similar proportions have been observed in this laboratory over a number of years.

Ramgren5 who included Rh-positive and negative donors in his investigations noted an increase in the number of Rh-negative per- sons amongst those with a high-titre anti-A. This could not be checked as part of the present series, bu t previous unrecorded observations have not indicated any such tendency.

The distribution of A, and A, amongst high-titre Group A donors was not investigated, but a small series of tests recently performed by the author €or another purpose indicates that the A,/A, distribution amongst donors with serum selected as being of low titre is not differ- ent from tha t in the general population.

It is possibIe that the higher percentage of high-titre anti-A occur- ring in Group B persons may be due to the fact that substances allied to A are widely distributed in nature, e.g., in bacteria, in plants, the Forsmann antigen in animal tissues, etc, and also most vaccines and therapeutic anti-sera contain some sort of A-like antigen. Accidental immunisation by these may result in the formation of immune anti-A, with a corresponding increase in the titre of saline agglutinin. This would fit in well with the fact that in Group 0 individuals the titre of anti-A is generally greater than that of anti-B. No explanation of the balance of absolute figures is apparent.

Anti-B Agglutinins in Blood Donors in the South-West of England

Acknowledgement

421

I am indebted to Dr G.H. Tovey for permission to publish the figures quoted.

Summary

Figures relating to the distribution of high-titre anti-A and anti-B agglutinins amongst 5000 blood donors in the South-West of England are given, and a possible cause for the unequal balance of the two sera suggested. It is shown that the absolute figures for the two sera are almost identical.

Risurn6

La frdquence d'individus avec des agglutinines anti-A ou anti-B A titre Clev6 parmi 5000 donneurs de sang dans le Sud-Ouest de l 'hgleterre a Ctd calculke: L'anti-A B haut titre est considerable- ment plus frequent chez les individus du groupe B que l'anti-B Blevd chez les donneurs du groupe A. Les raisons possibles de cette divergence sont discutees. Les frequences absolues (par rapport au total des donneurs examines) des deux types de serum sont presque identiques.

Zusamrnenfassung

Bei 5000 Blutspendern aus Siidwest-England wurde die Haufigkeit von Seren mit hochtitrigen Anti-A und Anti-B Isoagglutininen er- mittelt. B-Individuen verfiigen wesentlich haufiger iiber hochtitrige Isoagglutinine als A-Individuen. Wenn man die ungleiche Haufigkeit dieser beiden Blutgruppen beriicksichtigt, verwischt sich dieser Unter- schied. Die Gesamtausbeute an hochtitrigen Anti-A und Anti-B-Seren ist ungefahr gleich grol3.

References

Boyd, R? C.: Genetics and the Races of Man, Blackwell Scientific Publications, Oxford 1950, p. 244.

* Farr, A.D., and D. C. Godwin: J. med. Lab. Technology 13, 8, 1955.

' Rainsford, S.G., and W . T . J . Morgan: Determination of blood groups. Use of

Ramgren, 0.: High isohaemagglutinin titre in blood groups A and B. Lancet

McCrudden, R.J.G.: Personal communication, 1956.

rabbit anti-sera. Lancet, 1946/I, 154.

1954/I, 782.

Author's address : Dr. A. D. Farr, Regional Transfusion Centre, Rhydlafar near Cardif, S . Wales (Great Britain).