DURATION OF FIRST REMISSION IN LEUKAEMIC RECIPIENTS OF LEUCOCYTE‐POOR BLOOD COMPONENTS

The use of leucocyte-poor (LP) blood components has been associated with a reduction in the prevalence of alloimmunization to HLA antigens shown by recipients of standard blood, and the related occurrence of immunological refractoriness to random donor platelet transfusion (Andreu et a/ , 1988). Notwithstanding this and other benefits of LP blood transfusion, it was of concern to read the report of Tucker et a1 (1 989) who suggested that leukaemic recipients of LP blood components might lose a beneficial ‘graft-versus-leukaemia’ effect exerted by transfused leucocytes. Therefore, we were pleased to read that Norol et a1 (199 1 ) failed to show the presence of this effect in acute myeloid leukaemia (AML) patients, thus supporting the results of our prospective investigation on the same issue (Rebulla et al, 1990) and of that of Lopez et af (1 990). However, Norol et (11 contend that two flaws prevent the validity of our study: first, we did not separate AMI, from acute lymphoid leukaemia (ALL) patients for the evaluation of time to relapse: second, they interpret that we did not report the total amount of lencocytes administered to our LP patients, and that our results with the Imugard filter used for leucocyte depletion do not agree with other studies, including that by Brubaker & Romine (1988). Our answers to this criticism are as follows. First, there is no need to separate AML from ALL, provided they are similarly distributed among recipients of LP or Standard (S) blood components, as was the case in our study. Second, we clearly state that our L P recipients received red blood cells and platelets containing no detectable leucocytes in 8 3% and 73% of cases respectively, and that in all other cases less than 5 x 1 O6 contaminating leucocytes per transfusion were given. It is therefore very easy to compare these figures with the well-known figure of about 2000-3000 x 10” and 50100 x 10h leucocytes contained on average in S red blood cells and platelets respectively. As far as discrepancies in leucocyte counts obtained after Imugard filtration in our study compared to other reports, it is well known that these can be caused by differences in the type and age of blood components used for filtration and the method of counting. As far as thislatter, it has been clearly shown that the manual method that we used is much more accurate than others based on automated counters such as the one used by Rrubaker & Komine (Milner et a/, 1982). For the reasons above we believe that our data validly contribute to support the data of Lopez et al ( 1 990) and of NoroI et al(1991). which indicate that leucocytes contained in S blood components do not show a demonstrable antileukaemic effect, and that leukaemic patients may benefit from LP blood tranfusion.