Final answer:
The IL-17 (option 4) family is the most recently discovered group of cytokines that contributes to both innate and adaptive immunity, with IL-17A being an important member in fighting bacterial and fungal infections.
Step-by-step explanation:
The family of cytokines that is the most recently discovered and contains cytokines that contribute to both innate and adaptive immunity is the Interleukin 17 (IL-17) family. Interleukins are a group of cytokines that play a crucial role in the immune system by mediating interactions between leukocytes and bridging innate and adaptive immune responses. The IL-17 family is known for its role in inflammation and host defense, and like other cytokines, the IL-17 cytokines are involved in cell signaling, which influences the function of immune cells. The most prominent member of this family, IL-17A, is particularly significant in fighting off extracellular bacteria and fungi.