White Blood Cells Known as CD16+ Monocytes Appear Linked to Fibrosis in SSc Patients

The number of white blood cells known as CD16+ monocytes is notably greater in the blood of systemic sclerosis (SSc) patients when skin or lung fibrosis is present, researchers said, recommending that these cells be studied further to determine if they contribute to fibrosis development in SSc.

The study, “CD16-positive circulating monocytes and fibrotic manifestations of systemic sclerosis,” was published in the journal Clinical Rheumatology.

SSc is an autoimmune disease, meaning a patient’s own immune system attacks tissues in the body, in this case, connective tissues. Connective tissue supports, connects or separates different types of tissues and organs in the body. Its characteristic symptoms are the thickening of the skin and injury to small arteries.

SSc can also cause fibrosis, the formation of excess fibrous tissue. Pulmonary fibrosis, or fibrosis in the lungs, is a serious occurrence in some cases of SSc.

CD16+ monocytes are a type of white blood cell with a molecule called CD16 on their surfaces. Monocytes positive for CD16 are thought to be involved in diseases characterized by abnormal tissue remodeling, such as fibrotic disorders, and in inflammation.

To address whether the levels of CD16+ monocytes were linked to clinical manifestations of SSc, researchers analyzed 48 SSc patients and 23 healthy volunteers.

They found that the number of monocytes circulating in the blood, with or without CD16 on their surfaces, was higher in SSc patients than in healthy volunteers.

There are two forms of SSc: limited and diffuse. The limited form affects the skin of the face, hands, and feet only; the diffuse form may also involve organs, including the kidneys, heart, lungs, and the gastrointestinal tract. When the numbers of monocytes without CD16 were compared in patients with limited SSc (lSSc) to those with diffuse SSc (dSSc), they were found to be similar.

But numbers of CD16+ monocytes were higher in people with dSSc compared to those with lSSc, and also compared to healthy volunteers.

In fact, the higher the numbers of CD16+ monocytes in the blood, the more severe was skin fibrosis in SSc patients, the researchers reported, finding a “significant” correlation between these two. Higher numbers of CD16+ monocytes were also present in patients with pulmonary fibrosis.

“These results suggest that CD16+ monocytes are associated with the main fibrotic manifestations of SSc and their role in the pathogenesis of fibrosis in this autoimmune disorder should therefore be further considered,” the authors concluded.