An integrated human immunoglobulin germline resource linking allele diversity to expressed repertoire structure.

Human immunoglobulin (IG) loci are highly polymorphic, yet existing germline resources remain noisy and incomplete, limiting our ability to link inherited variation to antibody repertoires. Here, we integrate high-fidelity long-read genomic sequencing with matched adaptive immune receptor repertoire sequencing (AIRR-seq) to construct HUSA, a population-scale, evidence-resolved germline resource. Using a conservative allele inference framework, HUSA expands current references more than three-fold, identifying over 1300 alleles while preserving allele-level evidence provenance across genomic and repertoire data. By linking genotype and expressed repertoires within individuals, we show that coding-region similarity predicts the structure of adjacent recombination signal sequences and leader regions, revealing that IG alleles are organized as linked cis-regulatory units associated with differences in recombination context and allele usage. These results define key germline constraints shaping repertoire formation and establish a robust, genotype-aware foundation for the analysis of immune receptor repertoires.