Levels of antibodies that the body produces against two proteins may help doctors predict the risk of bronchiectasis patients developing rheumatoid arthritis, a study reports.
The proteins are calreticulin, or CRT, and citrullinated calreticulin, or citCRT. Bronchiectasis is a lung disease whose hallmark is bronchial tube damage from inflammation or other causes.
The study was published in the journal International Journal of Biochemistry and Cell Biology. Its title was “Heightened autoantibody immune response to citrullinated calreticulin in bronchiectasis: Implications for rheumatoid arthritis.”
Rheumatoid arthritis, or RA, is an autoimmune disease characterized by intense tissue inflammation and joint destruction. But it can also affect other organs, such as the lungs, eyes and heart.
With rheumatoid arthritis, the body’s own antibodies — which are supposed to fight disease — can attack tissue as if they were invaders, damaging them.
CRT and one of its forms, citCRT, trigger the inflammation associated with rheumatoid arthritis by binding to other molecules in cells.
“Recently we have demonstrated that RA patients with BR [bronchiectasis] have increased disease activity, severity and autoantibody positivity and that RA autoantibodies are predictors of RA developing in BR patients,” the researchers wrote.
“We studied RA patients with and without BR to assist in our understanding of the prevalence of citCRT in individuals and the autoantibody response” to CRT and citCRT “in association with other risk factors,” such as lung disease, they wrote.
The team analyzed levels of the autoantibodies that the body produces against CRT and citCRT in blood samples from 388 people. Fifty were rheumatoid arthritis patients, 122 bronchiectasis patients, 52 bronchiectasis patients who also had rheumatoid arthritis, 87 asthma patients, and 77 healthy subjects.
Eighteen percent of bronchiectasis patients with or without rheumatoid arthritis had CRT antibodies in their blood. And 35 percent of bronchiectasis or RA patients had citCRT antibodies, compared with 58 percent of patients with both diseases.
Importantly, three out of four bronchiectasis patients who developed rheumatoid arthritis over the next 18 months had citCRT antibodies in their blood.
The findings suggest that the molecules may be detected months before the onset of RA, making them biomarkers of the risk of someone developing the disease.
“We present for the first time early insights into the possible role of CRT and anti-citCRT in BR [bronchiectasis] and RA,” the researchers wrote. Scientists are likely to be interested in the role that citCRT antibodies play in predicting the progression of rheumatoid arthritis, they wrote. And therapies targeting the proteins could evolve from the findings.