GCA has both vascular and extravascular components. In the extravascular phase, innate immune cells like monocytes and neutrophils are triggered, and innate, pro-inflammatory cytokines are released. There is an induction of hepatic acute phase proteins, such as C-reactive protein, mannose-binding protein, ferritin and others. This may result in an inflammatory amplification loop.
“We need to understand the role of hepatic acute phase proteins in GCA and polymyalgia rheumatica, and we need to know what they do in the disease process. Right now, we do not know,” Dr. Weyand said.
Tocilizumab, an IL-6 inhibitor, is approved by the U.S. Food and Drug Administration to treat GCA, but unanswered questions, including whether biomarkers for disease activity are lost after therapy blocks IL-6 and if the tissue-protective functions of acute phase proteins are also blocked by treatment, are important for GCA patients, said Dr. Weyand.