Il-10 Polymorphism and TGF-β Haplotypes Are Associated with Rejection of Graft in Children with Beta Thalassemia Major Undergoing Matched Related Bone Marrow Transplantation (BMT).

Th2 cytokines, IL-10 and TGF-β have immunoregulatory functions that can affect allograft acceptance. We have evaluated the correlation between IL-10 (-1082, -819, -592) and TGF-β codon 10C>T and 25G>C polymorphisms {(haplotype: TT/GG, TC/GG, high production); (haplotype: TC/GC, CC/GG, TT/GC, intermediate production); (haplotype: CC/GC, CC/CC, TT/CC, TC/CC, low production)}and graft rejection in 129 patients with β thalassaemia major who underwent matched related alloBMT. Patients who expired before day 15 (n=9) and for whom DNA samples was unavailable (n=18) were excluded from this study. None of these patients had graft rejection. Of the 102 patients who were evaluated, 73 (72%) patients received conditioning with Bu (16 mg/kg) / Cy (200 mg/kg) with ALG while 29 (28%) patients received Bu (600 mg/m2) / Cy (200 mg/kg) without ALG. All patients received unmanipulated bone marrow and standard cyclosporine / short course methotrexate regimen as prophylaxis against GVHD. Patients who died before day 21 after transplant (n=2) without achieving ANC >500/mm3 were not evaluated for engraftment. 9 out of 102 patients rejected their graft. Apart from the immunogenetic markers, the effect of other risk factors for rejection like recipient and donor age, sex mismatch, conditioning regimen, cell dose and Lucarelli class were also analyzed. Of these, only increasing donor age was found to mildly increase the risk of rejection (RR=1.06; p=0.019; 95% CI-1.01–1.1). Donor TGF-β haplotypes associated with intermediate or low production and IL-10 polymorphism accounting for low production were found to very significantly increase the risk of graft rejection (Table). TGF-β and IL-10 are essential for both development and the effector function of CD4 regulatory T cells which are important for tolerance induction. Therefore, it is possible that genotypes associated with lower production of these cytokines might contribute to increased graft rejection. We have previously reported that rejection in children with β thalassemia major is influenced by pharmacokinetics of busulfan and cyclophosphamide and genes implicated in their metabolism (BMT 2005 36, 839–845). We conclude that rejection of graft in this condition appears to be a multifactorial event affected not only by pharmacogenetics of the drugs used for conditioning but also by various immunogenetic factors.