Figure 1

Normal immune responses depend on appropriate levels of immune suppression. This schematic depicts three potential outcomes of an infection and the resulting inflammatory responses on the basis of varying the level and dynamics of immune suppression. (A) In a normal immune response, the infectious agent stimulates an early inflammatory response that begins to control the infection before immune suppression begins. As the infection is cleared, inflammation decreases while immune suppression continues to increase, resulting in the resolution of inflammation and return to homeostasis. (B) An immune response with delayed or weakened immune suppression leads to increased inflammation and impaired resolution despite the absence of the eliciting infectious agent. If unresolved, this scenario would lead to severe acute inflammation and death. (C) Early and/or increased suppression may inappropriately lower inflammation and prevent clearance of the infectious agent. Depending on the nature of the infection and the balance between inflammation and suppression, this result could lead to morbidity caused by the infectious agent, a chronic state of inflammation and/or higher baseline suppression toward the next inflammatory stimulus. Infection; inflammation; immune suppression.