HLA alleles shape distinct biases in the usage preferences of TCR Vβ segments

T cells must co-recognize peptide and HLA, yet the extent to which this specificity is shaped by germline-driven TCR–HLA contacts has remained difficult to quantify. Leveraging population-scale TCR β repertoires linked to donor HLA genotypes inferred using validated imputation models, we construct allele-specific TCR V β gene usage profiles and normalize them to repertoire-wide baselines to derive interpretable HLA-V β preference vectors. We demonstrate that different HLA alleles shape distinct biases in the usage frequency of V β gene segments among the public TCRs that engage those alleles: certain V β genes are over-represented for particular HLA alleles. Similarities in HLA amino-acid sequence predict similarities in both their V β preferences and peptide-binding motifs. A residue-level analysis disentangles HLA positions primarily associated with V β engagement from those primarily associated with peptide motifs; the V β -associated HLA positions localize to canonical TCR-facing helices, whereas peptide-associated HLA positions track binding pockets, revealing distinct molecular routes by which HLA polymorphism shapes the TCR and peptide sides of recognition. CMV exposure stratifications confirmed these V β preference vectors are not explained by any shift of repertoire composition associated with a dominant infection. Together, these data support that germline-driven constraints set the landscape of TCR–HLA compatibility. These HLA-specific TCR V β biases are a biological prior that provide a foundation for better understanding of TCR-pHLA specificity as a whole and should be accounted for in future evaluation of any TCR-pHLA specificity prediction methods.