FREQUENCY OF DONOR CYTOTOXIC T-CELL PRECURSORS DOES NOT CORRELATE WITH OCCURRENCE OF ACUTE GRAFT-VERSUS-HOST DISEASE IN CHILDREN TRANSPLANTED USING UNRELATED DONORS

Bone marrow transplantation (BMT) from unrelated volunteers is frequen tly associated with both increased incidence and increased severity of acute graft-versus-host disease (GVHD). In the last years, it has bee n suggested that the analysis of the frequency of cytotoxic T lymphocy te precursors (CTLp) of unrelated HLA-matched donors can be used to de tect disparity for HLA class I antigens and as a predictive test for d evelopment of severe GVHD. In this report, we summarized our experienc e regarding 20 pediatric patients affected by various hematological di sorders, receiving allogeneic BMT from unrelated donors, HLA class I a nd II antigens of donor/recipient pairs were determined by means of se rological typing, whereas molecular typing of HLA-class II antigens of patients and their potential donors was performed using PCR-SSP and P CR-fingerprinting techniques. CTLp values, estimated using limiting di lution analysis, were high (range, 1:7000-1:40,000) in 9 of 20 patient s, while the other 11 children had low or undetectable levels (<1:100, 000) of CTL precursors. CTLp frequency was compared with the incidence and severity of GVHD observed after BMT. Our data demonstrate that th e frequency of donor CTLp does not statistically correlate either with the occurrence of clinically significant acute GVHD or with disparity for HLA-class II molecular typing between donor and recipient. In par ticular, 4 of the 10 evaluable patients with an undetectable CTLp freq uency developed grade IV, III, II, and IV acute GVHD, respectively. Al though the limited number of subjects studied does not allow us to dra w any firm conclusion, our data suggest a certain caution in consideri ng this test suitable for the selection of potential donors.