The session on T cell and B cell activation will provide an overview of the molecular and cellular mechanisms underlying lymphocyte activation, including antigen recognition, co-stimulation, and signaling pathways. Emphasis will be placed on the differentiation of effector and memory cells and their roles in adaptive immunity. Clinical implications include understanding the pathogenesis of autoimmune diseases, immunodeficiency disorders, vaccine responses, and the rationale behind immunotherapies targeting T and B cells in conditions such as rheumatoid arthritis, lupus, and certain cancers.