The 1949-1978 period saw rapid maturation of antibody-based diagnostic technologies, with emphasis on enzyme-labeled antibodies and non-radioactive readouts that increased sensitivity and scalability for clinical testing. Techniques such as early immunoassays, radioimmunoassays, and immunofluorescence expanded diagnostic reach across infectious disease, endocrinology, and cancer research, unifying methodological approaches around antibody-antigen interactions and detectable labels. Historical Significance: The foundational integration of immunoassay principles established a durable paradigm for modern diagnostics, enabling safer, faster, and more accessible biomarker measurement and setting the stage for the enzyme-linked immunosorbent assay and related immunodiagnostic platforms that dominate the field today.