Unrelated cord blood transplantation in pediatric patients: a report from Saudi Arabia

In unrelated cord blood (UCB) transplantation, survival has been shown to correlate with the degree of HLA matching. Thus, to extend transplant access to different ethnic backgrounds, many western UCB transplantation banks now encourage donation from non-Caucasians. Until recently, Saudi Arabia did not have a national UCB bank. In this study we report our experience in UCB transplantation in children using units procured from western cord blood banks. A total of 97 children underwent unrelated UCB transplantation at King Faisal Specialist Hospital and Research Center (KFSHRC), of which 95 were of Arab ethnicity. A total of 30 patients had malignant disorders, 25 patients had non-malignant hematological disorders and 42 patients had inborn errors. Conditioning was according to disease, with six patients receiving reduced-intensity regimens. In all, 46 patients received one-Ag-mismatched units and 51 received two-Ag-mismatched units. Engraftment occurred in 93% of patients, the 100-TRM was 15%, acute GVHD developed in 20% of patients and chronic GVHD occurred in 9% of patients. The 5-year OS and EFS estimates were 52 and 43%, respectively. The search for UCB transplantation units for Saudi patients in western banks yielded reasonably compatible units for our patients; the results are consistent with published data. Our data are encouraging for UCB transplant programs in countries in which there are no national UCB transplantation banks.

Mutations of CD40 gene cause an autosomal recessive form of immunodeficiency with hyper IgM

CD40 is a member of the tumor necrosis factor receptor superfamily, expressed on a wide range of cell types including B cells, macrophages, and dendritic cells. CD40 is the receptor for CD40 ligand (CD40L), a molecule predominantly expressed by activated CD4(+) T cells. CD40/CD40L interaction induces the formation of memory B lymphocytes and promotes Ig isotype switching, as demonstrated in mice knocked-out for either CD40L or CD40 gene, and in patients with X-linked hyper IgM syndrome, a disease caused by CD40L/TNFSF5 gene mutations. In the present study, we have identified three patients with an autosomal recessive form of hyper IgM who fail to express CD40 on the cell surface. Sequence analysis of CD40 genomic DNA showed that one patient carried a homozygous silent mutation at the fifth base pair position of exon 5, involving an exonic splicing enhancer and leading to exon skipping and premature termination; the other two patients showed a homozygous point mutation in exon 3, resulting in a cysteine to arginine substitution. These findings show that mutations of the CD40 gene cause an autosomal recessive form of hyper IgM, which is immunologically and clinically undistinguishable from the X-linked form.