B cells and T cells are white blood cells (lymphocytes) for adaptive immunity, but B cells make antibodies (humoral immunity) to neutralize pathogens, while T cells directly kill infected/cancerous cells or help coordinate the immune response (cell-mediated immunity). Both originate in bone marrow, but B cells mature there, whereas T cells travel to the thymus to mature. B Cells (B Lymphocytes) Primary Role: Produce antibodies (proteins) that tag pathogens (bacteria, viruses) for destruction or