Final answer:
Pyrogen is not a signaling protein that regulates interactions between cells; cytokines, interleukins, and complement proteins are indeed signaling molecules involved in cell regulation and immune responses.
Step-by-step explanation:
The signaling proteins that regulate interactions between cells include cytokines, interleukins, and complement proteins. The only option provided that is not a signaling protein is pyrogen. Cytokines serve as chemical messengers regulating cell differentiation, proliferation, gene expression, and cell trafficking to mediate immune responses. Interleukins are a subclass of cytokines that are essential in hematopoiesis (the formation of blood cells), immunity, and inflammation. Complement proteins are part of the immune system that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells.