Figure 2.

The immune response in healthy individuals undergoes a cycle of activation and contraction. This graph illustrates the trajectory of a normal immune response. Detection of a pathogen or threat to human health initiates immune activation and subsequent inflammation, partly thanks to M1 macrophages. The mounting immune response causes clinical presentation of symptoms in the host, but this activation phase will not reach a state of hyperinflammation that jeopardizes the safety and life of the host. Once the immune system eliminates the threat, the body enters the contraction phase defined by an anti-inflammatory environment and elimination of excess immune cells that are no longer necessary for active defense. Lastly, differentiation of quiescent memory cells and wound healing occurs. This represents a return to a baseline or steady state of being, which can respond to future threats. Created with BioRender.com.