What is the Difference Between Positive and Negative Acute Phase Proteins

The key difference between positive and negative acute phase proteins is that positive acute phase proteins are a class of proteins whose concentrations in the blood plasma increase in response to inflammation, while negative acute phase proteins are a class of proteins whose concentrations in the blood plasma decrease in response to inflammation.

Positive and negative acute-phase proteins are two different types of acute-phase proteins. Acute phase proteins are a class of proteins whose concentrations in the plasma of the blood either increase or decrease in response to a particular inflammation. This response is called the acute phase reaction. The acute phase reaction includes fever, enhancing peripheral leukocytes, circulating neutrophils, and their precursors. Acute-phase proteins are sometimes called acute-phase reactants. However, strictly speaking, some acute phase reactants are polypeptides rather than proteins.

CONTENTS

1. Overview and Key Difference
2. What are Positive Acute Phase Proteins
3. What are Negative Acute Phase Proteins
4. Similarities – Positive and Negative Acute Phase Proteins
5. Positive vs Negative Acute Phase Proteins in Tabular Form
6. Summary – Positive vs Negative Acute Phase Proteins

What are Positive Acute Phase Proteins?

Positive acute phase proteins are a class of proteins whose concentrations in the blood plasma increase in response to inflammation. Positive acute phase proteins increase in concentration in the plasma in response to an inflammation generally within 1 to 2 days. Positive acute phase proteins are further categorized into major, moderate, or minor, based on the degree of increase. Anyhow, the magnitude of the increase of each acute phase protein varies based on the species.

Positive acute phase proteins usually serve different functions within the immune system. For example, C-reactive protein, mannose-binding protein, complement factors, ferritin, ceruloplasmin, serum amyloid A, and haptoglobin help to destroy the growth of different microbes. Other proteins such as serpins, alpha 2 macroglobulin, and coagulation factors normally give negative feedback on inflammatory responses. These factors mainly affect coagulation. Therefore, their procoagulant effect may limit infection by trapping microbes within the blood clots. Moreover, some of these proteins in the coagulation system contribute to the innate immune system by increasing vascular permeability and acting as chemotactic agents for phagocytic cells.

What are Negative Acute Phase Proteins?

Negative acute phase proteins decrease in concentrations in the blood plasma during inflammation. Examples of negative acute phase proteins may include albumin, transferrin, transthyretin, retinol-binding protein, antithrombin, and transcortin. The decrease in concentrations of these proteins can be used as markers of inflammation. Moreover, this reduction of concentration can occur rapidly within 24 hours or may occur over a period of days. The physiological role of decreased concentrations of these proteins is generally to save amino acids for producing positive acute phase protein more efficiently.

Albumin and transferrin are the most important negative acute phase proteins. The way their concentration decreases is multifactorial. These include decreased production by the liver, increased loss, or increased proteolysis.

What are the Similarities Between Positive and Negative Acute Phase Proteins?

• Positive and negative acute phase proteins are two different types of acute phase proteins.
• Both types of proteins are made up of amino acids.
• They are present in normal concentration prior to inflammation.
• Their measurement in blood plasma is a useful marker of inflammation in both medical and veterinary clinical pathology.

What is the Difference Between Positive and Negative Acute Phase Proteins?

Positive acute phase proteins are a class of proteins whose concentrations in the blood plasma increase in response to inflammation, while negative acute phase proteins are a class of proteins whose concentrations in the blood plasma decrease in response to inflammation. Thus, this is the key difference between positive and negative acute phase proteins. Furthermore, examples of positive acute phase proteins include c-reactive protein, mannose-binding protein, complement factors, ferritin, ceruloplasmin, serum amyloid A, haptoglobin, serpins, alpha 2 macroglobulins, and coagulation factors. On the other hand, examples of negative acute phase proteins include albumin, transferrin, transthyretin, retinol-binding protein, antithrombin, and transcortin.

The below infographic presents the differences between positive and negative acute phase proteins in tabular form for side-by-side comparison.

Summary – Positive vs Negative Acute Phase Proteins

Acute phase proteins are very important in diagnosing diseases. Positive and negative acute phase proteins are two different types of acute phase proteins. Positive acute phase proteins are a class of proteins whose concentrations in the blood plasma increase in response to inflammation, while negative acute phase proteins are a class of proteins whose concentrations in the blood plasma decrease in response to inflammation. So, this is the key difference between positive and negative acute phase proteins.

Reference:

1. Jain, Sachin, et al. “Acute-Phase Proteins: As Diagnostic Tool.” Journal of Pharmacy & Bioallied Sciences, U.S. National Library of Medicine, Jan. 2011.

Image Courtesy:

1. “Magnesium deficit, inflammation, oxidative stress, and aging” By Barbagallo, M.; Veronese, N.; Dominguez, L.J. (CC BY 4.0) via Commons Wikimedia
2. “Endocytic pathway of animal cells showing EGF receptors, transferrin receptors and mannose-6-phosphate receptors” By Matthew R G Russell – Own work (CC BY-SA 3.0) via Commons Wikimedia