Final answer:
Viruses and some intracellular bacteria induce dendritic cells to secrete interleukin 12, which stimulates the differentiation of T cells to Th1 cells, crucial in the immune response against intracellular pathogens.
Step-by-step explanation:
The direct answer to the question is: c:
Interleukin 12 (IL-12) is a pivotal cytokine secreted by dendritic cells that induces the differentiation of T cells into Th1 cells. Th1 cells play a crucial role in the immune response against intracellular pathogens, such as viruses and some intracellular bacteria. These cells secrete cytokines that stimulate not only the activation and proliferation of cytotoxic T cells, which are vital for killing infected cells, but also enhance the abilities of macrophages and neutrophils to eradicate intracellular pathogens.
Moreover, they promote NK cells to become more effective at killing target cells. It is important to note that other cytokines, such as tumor necrosis factor alpha, gamma interferon, and perforin play different roles in the immune response with gamma interferon being involved in warning nearby uninfected cells of a viral infection, and perforins being part of the cytotoxic arsenal used by NK cells and cytotoxic T cells to induce apoptosis in infected or abnormal cells.