Which statement best describes the clinical use of immune checkpoint inhibitors?

• A. Vaccination strategies to prime antibody responses
• B. Blocking inhibitory pathways to boost T cell activity against tumors
• C. Suppressing autoimmunity by depleting T cells
• D. Enhancing phagocytic activity of neutrophils

Answer: (B)

Immune checkpoint inhibitors work by releasing the brakes on T cells. In many tumors, T cells become inhibited by checkpoint molecules such as CTLA-4 or PD-1 engaging their ligands, which dampens the anti-tumor response. Blocking these inhibitory signals restores T cell activation, allowing them to proliferate, secrete cytokines, and attack cancer cells. This approach aims to boost the adaptive immune response against tumors, rather than to prime antibodies, suppress autoimmunity by removing T cells, or enhance phagocytosis by neutrophils. Drugs that do this include PD-1 or PD-L1 inhibitors and CTLA-4 inhibitors, which are used across several cancers, sometimes with immune-related side effects from heightened T cell activity.