Immunogenetics explores how genetic variation influences immune responses, shaping susceptibility to infections, autoimmunity, and treatment outcomes. This book fuses molecular genetics with immunology to explain HLA associations, single-gene immunodeficiencies, and polygenic risk for immune disorders. It reviews techniques from GWAS to functional genomics and interprets how findings translate into diagnostics and personalized therapies. Case chapters highlight examples where genetic insight changed clinical management, such as transplant matching and targeted immune modulation. Readers gain both conceptual frameworks and practical approaches for integrating genetic data into clinical and research workflows.