A predominance of HLA-B-restricted responses has been observed in HIV [36], measles [37] and mycobacterial [38] infections and was indeed suggested in an earlier study of virus carriers using EBV epitope peptides [39]; the effect has been linked to the greater heterogeneity of B alleles and to the ability of individual HLA-B proteins to accommodate a wider range of peptide sequences [40]. This evidence concerns the gene HLA-B and measles.