Immune System

A patient can be immunocompromised because a barrier is broken, neutrophils are missing, antibodies are ineffective, or T-cell coordination is impaired. Those deficits do not produce the same clinical picture, so the first nursing question is not simply whether infection is present; it is which part of host defence is failing and how that changes the patient’s risk. Innate defences act immediately, while adaptive defences provide antigen-specific antibodies, cellular responses, and immune memory. The distinction explains why a patient with neutropenia may deteriorate rapidly from a small bacterial exposure, why an antibody-deficient patient may have recurrent respiratory infections, and why an immunocompromised patient may show little redness or fever despite serious infection. It also guides safe decisions about vaccines, IVIG, surveillance, and escalation.