The CD19 and MS4A1 (CD20) genes, located on chromosomes 16p11.2 and 11q12.2 respectively, encode two canonical B-cell lineage-specific surface antigens. CD19 functions as a critical signal transduction component of the B-cell receptor co-receptor complex, thereby modulating B-cell activation, differentiation, and proliferation. CD20, a four-transmembrane domain phosphoprotein, serves as a store-operated calcium channel essential for B-cell cycle progression and humoral immune responses. Together, these molecules are indispensable for normal B-cell development and immunological function.The clinical relevance of CD19 and CD20 extends beyond basic immunology. Their high and stable expression on the surface of most B-cell malignancies has established them as primary targets for immunotherapy, including chimeric antigen receptor (CAR) T-cells and monoclonal antibodies (e.g., Rituximab). However, lineage plasticity and antigen loss represent major resistance mechanisms, often leading to post-therapeutic relapse. Consequently, dual targeting of CD19 and CD20 has emerged as a promising strategy to mitigate antigen escape and improve durable responses, with multiple bispecific CAR-T constructs currently in preclinical and clinical development.