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Trans[us. ScL Vol.16, No.2, pp. 115-119, 1995 Copyright © 1995 Elsevier Science Ltd

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Clinical and Laboratory Aspects of TA-GVHD with Reference to

Perinatal Patients and Gamma-irradiated Red Cell

Components R. M. W a r w i c k

M. J. S e g h a t c h i a n S. P e n n y

M. V i c k e r s C. M. Har r i s

J. F. A. S t iva la

INTRODUCTION AND OBJECTIVES

There is a small but finite risk of TA- GVHD in recipients of cellular blood components . This risk is increased when the donor and recipient are related, 1'2 in relatively homogeneous populat ions wi th a high rate of HLA homozygosity or when the recipient has cellular immune deficiency. There are, nevertheless, no case reports of TA- GVHD occurring in subjects with AIDS, perhaps because the donor lymphocytes become infected with HIV.

Worldwide, perinatal recipients common ly receive blood componen t s that are irradiated. The basis for this practice, for unrela ted donations, in immune competent perinatal patients is considered here. In addition, we address the potassium egress from irradiated red cell components in order to assess the suitability of these components for use in various clinical indications. The effect of irradiation on the red cell potas- sium egress, post-storage, compared to the identical control, is briefly addressed.

Quality Assurance, North London Blood Transfusion Centre, Colindale Avenue, London NW9 2BG, U.K.

LITERATURE SURVEY AND COMMENTARY ON PERINATAL

INDICATIONS FOR IRRADIATED BLOOD COMPONENTS

The li terature underlying the practice for gamma irradiation of random unre- lated cellular components for perinatal transfusions, where the recipient is immunologically normal, shows a pau- city of reported cases of TA-GVHD in the perinatal setting. This may represent either the rarity of the disorder, under- reporting, the already established prac- tice of irradiation in this s i tuat ion or lack of recognit ion of cases of TA-GVHD.

Intrauterine Transfusions (IUT)

There is a single disputed case report 3 underlying the practice of irradiation of random, unrelated cellular blood com- ponents for IUT. In this context, irradi- ation is performed for theoretical con- siderations including immaturi ty of the fetus as the recipient and the use of fresh donat ions containing viable lympho- cytes. In common with adults, the pre- sumptive risk of TA-GVHD following IUT relates to the prevalence of HLA homozygosity in the donor population and HLA homogeneity in the population

Ts16:2-c 115

116 Transfus. Sci. Vol. 16, No. 2

in general. These factors will determine the likelihood of a heterozygous recipi- ent fetus sharing an HLA homozygous donor haplotype.

Intrauterine Transfusions (IUT) and Subsequent Exchange Transfusion (ET)

TA-GVHD following IUT and sub- sequent ET has been described in four cases 4-6 in the literature, although the number of infants who have been sub- jected to both types of transfusion must be very small. In three of these cases s'6 the ET donor lymphocyte origin of TA- GVHD suggests that IUT is immune suppressive. This gives weight to the need for leucodepletion of cellular com- ponents for IUT z because immune modulation appears to be due to the presence of contaminating white cells whether or not they are irradiated. In order to remove rather than prevent pro- liferation of these white cells, effective lencodepletion is recommended.

Exchange Transfusion Alone

Case studies do not support irradiation of blood for ET in the preterm infant, there being only three cases described. 8-~° The case for term infants is also flimsy with two cases described, 6,'1 which should be viewed in the context of the many thousands of exchange transfu- sions that took place prior to effective anti-D prophylaxis in the early 1970s. Therefore irradiation for this indication is highly debatable.

Top-up Transfusions

Even though it is common for multiple transfusions to be administered to neo- nates on Special Care Baby Units, there is only one case report of TA-GVHD in a preterm infant from an unrelated donor. This apparently immune competent, 25 weeks' gestation infant developed TA- GVHD following three top-up transfu- sions from a single donor, amongst a total of eleven transfusions. This donor's lymphocytes engrafted despite

donor/recipient HLA disparityJ 2 There- fore there is insufficient evidence to recommend irradiation of components for immune competent infants receiving top-up transfusions. The same applies for term infants including transfusion of infants undergoing cardiac surgery. Cel- lular components need only be gamma irradiated when cardiac defects occur together with cellular immune defects, although a case has followed extracor- poreal membrane oxygenation. '3

LABORATORY ASPECTS AND VALIDATION OF IRRADIATED

RED CELL COMPONENTS

Laboratory Protocols and Potassium Egress from Red Cell Components

To assess the potential risk of transfus- ing components with various supernat- ant potassium concentrations for differ- ent clinical settings, non-irradiated control components were compared with the identical paired gamma irra- diated [minimum of 25 Gy] components of the same origin for the rate of potas- sium egress. Components evaluated were whole blood for exchange transfu- sion, buffy coat depleted red cells in optimal additive solution IRBC in OAS) for top-ups, and packed red cells of HCT 90% for IUT. In addition huffy coat depleted RBC in OAS were investigated when irradiated either on day 1 or day 4. All components were studied over the period of their shelf life. The values reported are the means of 5 pairs.

It should be noted that the values reported here are over-estimates because sampling from the components was per- formed sequentially on the same units and therefore were progressively volume depleted and subjected to repeated hand- ling. These conditions are not experi- enced by units issued directly for clin- ical purposes. Moreover, the laboratory equipment used for the estimations of potassium is validated for physiological and clinical potassium levels, not for the high values seen in stored blood components.

TA-GVHD and Perinatal Patients and Irradiation 117

For red cells, HCT 90% for IUT, the rise in [K ÷] was very rapid in the first 2 days, subsequently reaching a plateau wi th in a few days, then remaining at similar levels until 28 days, presumably due to equi l ibrat ion wi th the red cell internal mil ieu. Despite the rapidly rising and high levels of supernatant [K+], the total K + in the irradiated packed red cell componen t s was low, even after storage (see Fig. 1 ). However, occasional unexplained fetal bradycar- dias associated with IUT are seen, and together with the high supematant pot- assium levels in concentrated red cells suggests that caution is needed whilst experience is accumulated in this field.

Irradiated buffy coat depleted red cells in OAS, haematocrit 60--64%, is only required for i m m u n e suppressed neonatal subjects for top-up purposes. Potassium levels progressively increased in the units irradiated either on day 1 or day 4. Small volume transfusions pose no risk of hyperkalaemia. No change to the normal expiry time of this type of componen t for small vo lume transfu- sions is required.

Whole blood for exchange, haem- atocrit 37-42%. The [K +] approximately doubled in the irradiated componen t compared to the non-irradiated counter- part. However, [K +] was not the criterion for de te rmin ing the shelf life of non-

irradiated blood for ET, therefore a shortened shelf life for the irradiated counterpar t may be unnecessar i ly proscriptive.

Percentage Changes in Potass ium Concentration Due to Irradiation of

Red Cell Components

In this pair control led study, vari- ations between individual components were eliminated because pairs of units were pooled together, mixed and then split into two identical halves. By this means the percentage increase in super- natant potass ium in irradiated uni ts compared to the non-irradiated controls reflected solely the effects induced by irradiation administered at day 1 or day 4 and the subsequent changes with stor- age. Figure 1 summarizes the results obtained.

Concentrated red cells, haemato- crit 90%. The percentage increase in potassium leak due to irradiation in this component was very rapid in the first day reaching 350% of the control (3-fold increase) but was virtually the same as the control levels by 28 days (see Fig. 1). Presumably the rapid equilibration of potass ium concentra t ion between the small vo lume of supernatant and the large surface area of the red cell may contribute to the initial fast rate of pot-

350 - -

300 - -

250-

o 2 0 0 - -

150 --

I lOO

o

• Whole blood I ~J¢~'O~. t3 Conc RBC ! I ~ ~ . . . O BCDRBCin OAS I / \ O .~ (irrad on day I) 4~ % " ~ . ~ 0 BCDRBCinOAS [ ~ ~ ~ (irrad on day 4) : \ I ' - - " - -

I

61 I I I 5 10 15 20 25 30

I 35

A g e (days)

Figure 1. % Changes in potassium in various irradiated red cells relative to identical non- irradiated control.

118 Trans[us. Sci. Vol. 16, No. 2

assium egress. Red cells in optimal additive solu-

tion. Extremely interesting observations were made concerning the comparison between the RBC in OAS when irradi- ated on day 1 and day 4. Whilst the rate of potassium egress in the two compon- ents were identical in their respective post-irradiation periods, the comparison of potassium levels of each compared to its own control was very different.

For cells irradiated on day 1, there was over a 3-fold increase compared to the control by day 3 post-irradiation. For the cells irradiated on day 4 the increase was about 2-fold for the same post- irradiation period (see Fig. 1). Over sub- sequent storage the ratios converged and reached a pla teau of approximate ly 200%. The mechanism of the different changes in po tass ium concen t ra t ion ratios in cells irradiated on day 1 or 4 is not clear but may be due to changes in RBC membrane structure with storage prior to irradiation. Further studies will be undertaken in this area.

Whole blood. The percentage rise in fresh whole blood closely followed the pat tem seen in RBC in OAS irradiated on day 4 th roughou t its shelf life, a l though the ini t ial rise was sl ightly higher.

CONCLUSION

There is no agreed rationale for the prac- tice of irradiation of blood components in the perinatal setting. The paucity of reported cases of perinatal TA-GVHD associated with blood transfusion from unrelated donors to immune competent subjects may be due to a combination of the etablished practice of irradiation, the rar i ty of the disorder and the under- reporting of cases. The current practice of irradiation of blood components for transfusions in the perinatal setting is founded on minimal clinical data except where ET follows IUT. On the other hand, it can be argued that irradiation is appropriately applied to the transfusion needs of perinatal patients who have the longest potent ia l post- t ransfusion life

ahead of them. However, the avoidance of TA-GVHD by gamma irradiat ion must be weighed against the disadvant- ages of i rradiated components . These include the reduced life span in vivo of red cell components with storage after irradiat ion. ~4 The superna tan t potas- s ium concen t ra t ion varies wi th the haematoc r i t of red cell componen t although the potassium load varies with the total volume of plasma infused. This may be very small in small vo lume transfusions and where the red cells are concentrated. However, this may have m i n i m a l cl inical significance except where the recipient has renal failure or is suscept ible to a po tass ium load, including massive transfusion.

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