Immune responses to infection.

The inflammatory and immune response to infection is a complex physiologic process targeted at removing foreign invaders, or pathogens, from the body. The initial inflammation that occurs may eliminate the pathogen, so that no infection results. If the inflammatory response is insufficient to remove the pathogen from the body, the acquired immune system becomes activated, stimulating the actions of T and B lymphocytes, which also attempt to eradicate the infectious pathogen. If this activity is successful, the body remains free of infection. If the pathogen remains viable in the body despite inflammatory and immune system actions, active infection ensues. The severity of the infection and the body's response depend on a multitude of factors including intactness of barrier defenses, immune competence of the host, virulence of the invading organism, and other underlying disease processes at work in the body. The critical care nurse must understand the inflammatory and immune responses to infection to appreciate the local and systematic effects of infection in the body and the rationale for treatment modalities.