White blood cells defend against infection through several specialized roles. Neutrophils rapidly respond to bacteria, engulfing and destroying invaders. Lymphocytes include B cells that produce antibodies and T cells that destroy infected or abnormal cells. Monocytes mature into macrophages, cleaning up debris and presenting antigens to activate other immune cells. Eosinophils combat parasites and modulate allergic responses, while basophils release histamine to promote inflammation. The coordinated action of these cells sustains immune surveillance and tissue repair. Understanding WBC function informs diagnosis of infections and immune disorders. For supply chain and clinical support, ceftriaxone distributors can advise on appropriate procurement and usage where indicated.