Acute phase proteins (APPs) are a group of proteins that are synthesized by the liver in response to inflammation or infection. These proteins play a key role in the body’s acute-phase response, which is a complex physiological process that occurs in response to injury, infection, or other types of stress.
The acute-phase response is characterized by a number of changes in the body, including fever, increased heart rate and blood pressure, and changes in the levels of certain blood proteins. The goal of this response is to mobilize the body’s resources to fight off the underlying cause of the stress or injury.
Acute phase proteins are typically divided into two main categories: positive acute phase proteins and negative acute phase proteins. Positive acute phase proteins are proteins whose levels increase in response to inflammation or infection, while negative acute phase proteins are proteins whose levels decrease during this response.
Examples of positive acute phase proteins include C-reactive protein (CRP), serum amyloid A (SAA), and fibrinogen. These proteins play a number of roles in the body’s response to inflammation, including activating the immune system, promoting tissue repair, and inhibiting the growth of certain pathogens.
Negative acute phase proteins include albumin, transferrin, and prealbumin. These proteins typically decrease in response to inflammation or infection, as the liver redirects its resources to the production of positive acute phase proteins.
The measurement of acute phase proteins in the blood can be used as a diagnostic tool in a number of different conditions, including infections, autoimmune diseases, and cancer. Elevated levels of acute phase proteins, particularly CRP, are often seen in conditions such as rheumatoid arthritis, inflammatory bowel disease, and cardiovascular disease, among others.
