Prevalence of C282Y and H63D mutations in the haemochromatosis (HFE) gene in Tunisian population

The studies of the HFE mutations: H63D and C282Y in North African populations have revealed the extreme rarity or even the absence of the C282Y mutation. We have examined 1140 chromosomes (570 Tunisian people) for the presence of the two HFE mutations by PCR-RFLP analysis. We have found that the allele frequencies are, respectively, 15.17% (+/-2.1%) for the H63D and 0.09% (+/-0.17%) for the C282Y. These results are consistent with the worldwide spread of the H63D mutation and the north European restriction of the C282Y. This study will be completed by determining whether homozygote trait for H63D and associated risk factors (beta thalassémia) can lead to iron overload in Tunisia.

Peptides bound to major histocompatibility complex molecules

Peptides are the means by which immune effector T cells recognize and defend against the foreign proteins of pathogens. T cell recognition of these molecules, however, is strictly dependent on peptide binding to the receptor-like molecules of the major histocompatibility complex (MHC) locus. The basic unit of recognition is a trimolecular complex consisting of the T cell antigen receptor, the MHC molecule, and the MHC-bound peptide ligand. The multistep process that culminates in MHC presentation of peptides to T cells begins in the last phases of protein catabolism. While the individual roles of many key molecules involved in peptide presentation have recently been defined, there still remain many questions regarding processing of proteins into MHC-bound peptides. This review summarizes the recent developments in peptide antigen processing for MHC molecules, with focus on how proteins are believed to be sampled and selected for degradation into peptides.