HLA-C and Menkes disease: TCR Vβ1 CDR1 haplotype usage in MD-resistant x MD-susceptible F1 birds by RNAseq indicated that the most commonly used CDR1 variant was unique to the MD-susceptible line, suggesting that selection for MD resistance in the MHC-matched model optimized the TCR repertoire away from dominant recognition of one or more B2 haplotype MHC molecules.