Acute phase proteins are a group of proteins produced by the liver in response to inflammation or injury. Their levels in the blood can increase or decrease rapidly during the acute phase of an illness, helping the body respond to stress, infection, or tissue damage. Common examples include C-reactive protein and fibrinogen, which play roles in the immune response and blood clotting. These proteins serve various functions, such as enhancing the immune system, promoting healing, and regulating inflammation. Measuring the levels of acute phase proteins can help healthcare professionals assess the presence and severity of inflammatory conditions, guiding diagnosis and treatment decisions.