Anti-cyclic citrullinated peptide (anti-CCP) antibodies

An autoantibody present in the blood of most patients with RA. Antibodies are proteins in blood that are an important part of the immune system, but this antibody is not usually present in healthy individuals. In both early and established RA, the test for anti-CCP is more specific to RA than that for rheumatoid factor.


Unlike antibodies, which are produced by the immune system to fight off foreign substances in the body, autoantibodies are produced by the immune system and attack the body’s own tissues.

Autoimmune disease

An illness that occurs when the body is attacked by its own immune system. The immune system is designed to destroy the body’s invaders, but people with autoimmune diseases often have antibodies (proteins) circulating in their blood that target their own body. Some examples of autoimmune diseases are RA, lupus, and juvenile (type 1) diabetes.


A characteristic of the body that can be objectively measured and evaluated and is an indicator of normal or abnormal process or disease. Types of biomarkers include proteins, genes, and other molecules. Cholesterol, for example, is a specific biomarker used to predict the risk of cardiovascular disease.

Bone remodeling

An ongoing process in which old bone is removed from the skeleton (resorption) and new bone is added (formation). These two stages of bone remodeling are usually part of a balanced cycle that maintains strength and consistency in bones.

C-reactive protein (CRP)

A protein that is a nonspecific biomarker for inflammation in the body. CRP is produced in the liver and its level is measured by testing the blood.

Erythrocyte sedimentation rate (ESR)

A common blood test that is used to indirectly measure inflammation in the body. Also called sedimentation rate, it measures the rate at which red blood cells (erythrocytes) settle to the bottom of a test tube.

Growth factor

A natural substance that has the ability to stimulate cellular growth and the specialization of different cells. Growth factors usually act by sending signals between cells and are important for regulating a wide range of processes in the body.


A gene that contributes to autoimmune disease. Carriers of the
HLA-DR genes have been shown to have an increased risk of RA.


A chemical messenger in the body that is released by one cell and sends a signal to another. Hormones travel through the bloodstream and bind to specific receptors that produce different responses. Hormones regulate many kinds of bodily functions.


The process in which white blood cells protect the body from infection, irritation, or other injury. However, sometimes these blood cells and their inflammatory chemicals can cause damage to the body’s tissues. The primary symptoms of inflammation are redness, warmth, swelling, and pain.


Proteins are essential components of all living cells and include numerous substances such as enzymes, hormones, and antibodies.


A protein that is located inside of a cell or on a cell surface and binds to a specific substance. In doing so, a receptor causes some sort of change in the cell’s activity.

Rheumatoid arthritis (RA)

RA is a chronic, systemic autoimmune and inflammatory disease that can affect multiple tissues and organs, causing joint damage (with pain, swelling, and stiffness in the joints) and leading to loss of function and disability.

Rheumatoid factor (RF)

An autoantibody present in the blood of many patients with RA. Higher levels of RF may indicate a higher risk of joint damage. RF can be present in some patients without rheumatoid arthritis. A blood test is used to detect the presence of RF.


This protein, which is produced by white blood cells, regulates immune cells, and produces inflammation.