The immune system has a variety of types of cells to fight infection, and different types of immune cells may attack different types of pathogens, independently or in sequence.  TNF-alpha is generated by the immune cells to create a higher level of inflammation, to attack chronic infection which is hard to reach with the normal immune response. High TNF-alpha is present in virtually all chronic diseases, which suggests the immune system is attempting to fight a chronic infection.  Inflammation occurs during an infectious cascade caused by immortal intracellular pathogens.  Inflammation is not an independent diagnosis.  Doctors tend to find inflammation and then call diseases inflammatory, without identifying the pathogens causing the inflammation and the  high TNF-alpha.