Which of the following is NOT a type of nonspecific immunotherapy?

C. Cancer vaccines are classified as a specific type of immunotherapy rather than nonspecific immunotherapy. This is because cancer vaccines are designed to elicit an immune response specifically targeting cancer cells. They typically work by introducing antigens associated with the cancer cells to the immune system, allowing it to distinguish between normal and malignant cells.

In contrast, nonspecific immunotherapies aim to enhance the overall immune response without directing it towards a specific target. Cytokines, for instance, are signaling proteins that can boost various immune responses, while checkpoint inhibitors work by blocking proteins that inhibit immune activation. Monoclonal antibodies can also act nonspecifically by marking cancer cells to enhance immune system recognition and response. However, their design can sometimes allow for targeted responses, but they form part of a broader nonspecific category when used to activate general immune pathways. This differentiation highlights why cancer vaccines are the correct choice for a type of immunotherapy that is not considered nonspecific.