Immune response to infection

The immune system is vital to the body's defence against bacterial, viral and fungal pathogens. An initial defence is provided by the innate immune system. The body's physical barriers are the first line of defence. If these barriers are breached a complex series of chemical, molecular and cellular interactions come into play to protect the body from further assault and tissue damage. Further mechanisms provide future protection through the development of acquired immunity.

Disruption of these intricate pathways results in a significant risk to the individual and is a common therapeutic challenge for clinicians. The immune system is a constant interplay of pathways that without balance can also lead to clinical compromise and morbidity, for example, through the extremes of overstimulation and development of an anaphylactic reaction or the failure to respond in an immunocompromised patient.

Recognition and appropriate management of over- and under-activity of the immune system are essential in reducing the risk of harm to patients.