What is the primary function of complement proteins in the immune system?

The primary function of complement proteins in the immune system pertains to their role in enhancing the ability of antibodies and phagocytic cells to clear pathogens. This system consists of a series of proteins that, when activated, can directly target pathogens and facilitate their destruction. One of the key mechanisms involves opsonization, where complement proteins coat pathogens, making them more recognizable and easier for phagocytes to engulf and eliminate.

Additionally, complement activation leads to the formation of a membrane attack complex that can directly damage bacterial cell membranes, enhancing the efficacy of the immune response. Overall, complement proteins work alongside antibodies and cells of the immune system to mount a more effective response against infections.

The other choices do not accurately represent the core function of complement proteins. Antibody production is primarily the role of B cells, direct killing of pathogens is performed by immune cells and certain complement mechanisms, and T cell stimulation involves different signaling pathways and is not a direct function of complement proteins. Thus, the correct answer highlights the key supportive role that complement proteins play in bolstering the immune response initiated by antibodies and phagocytes.