For millions worldwide, waking up with stiff, aching fingers that take hours to loosen is a daily battle — one waged by their own immune system. This is rheumatoid arthritis, a condition where the body’s defences mistakenly attack the joints they’re meant to protect.
Currently affecting about 18 million people worldwide, the Global Burden of Diseases, Injuries, and Risk Factors Study projected an alarming 80% rise in rheumatoid arthritis cases over the next 30 years.
Rheumatoid arthritis often strikes between ages 30 and 60, and women are thrice more likely to develop it than men. Scientists still don’t know exactly why but genetics, hormones, and environmental triggers like smoking or certain infections all appear to play a role.
While modern therapies have considerably improved patients’ quality of life, most patients are diagnosed only after the immune disruption has reached an advanced stage. The condition can affect the joints as well as lungs, the heart, eyes, skin, and many other organs. Chronic inflammation increases the risk of heart disease and causes fatigue, fever, and depression.
A new study in Science Translational Medicine, in which researchers mapped the hidden preclinical evolution of rheumatoid arthritis at the molecular level, could lead to the next leap in patient outcomes. The study has revealed that the immune cells are primed to become troublesome years before the first symptoms appear. In future, therefore, clinicians could potentially intervene early before joints are damaged.
Silent stage
One of the earliest warning signs of RA is the presence of anticitrullinated protein antibodies (ACPAs). These antibodies can appear in blood tests three to five years before the first clinical signs of arthritis. People who test positive for these antibodies but have no symptoms are labelled “at-risk individuals”, a definition adopted by clinical trials such as APIPPRA.
Not everyone in this group will develop RA. Roughly a third progress to the disease, while the rest remain symptom-free.
“Because they don’t have symptoms, it’s difficult to identify them early on,” Neha Singh, a rheumatologist at the University of California, Los Angeles, said. “You don’t want to treat everyone unnecessarily and risk side effects, but you also don’t want to miss early intervention opportunities.”
That uncertainty, who will progress and who won’t, remains a challenge.The new study set out to understand what tips the balance.
Researchers recruited 45 ACPA-positive at-risk individuals without symptoms, 11 patients with early-stage disease, and 38 healthy individuals. Over 18 months, sixteen participants developed clinical rheumatoid arthritis, which the researchers named “converters”. The team then compared immune profiles across all groups.
Using multi-omic approaches to examine plasma proteins, single-cell RNA sequencing, and chromatin accessibility, the study created a detailed map of how the immune system shifts from healthy to autoimmune.
One of the evident findings was that systemic inflammation is already present in the at-risk stage, even in people who feel healthy. Compared with controls, these individuals had higher levels of several inflammatory proteins such as CXCL3, CXCL5, and CXCL13, all chemokines that guide immune cells to inflamed tissue.
Importantly, these signals appeared in both those who later developed RA and those who didn’t, showing that “silent” immune activation preceded arthritis.
Primed state
The study paid particular attention to T cells and B cells, two major players in adaptive immunity. Naïve T cells, which are usually inactive until they encounter a new antigen, showed gene signatures indicating that they were already predisposed to activation. Epigenetic analysis revealed that DNA regions linked to the NFAT-calcium signalling pathway, a key driver of T cell activity, were more accessible in these individuals.
Naïve B cells expressed early signs of switching towards antibody types associated with inflammatory responses, particularly IgG3. In functional tests, B cells from at-risk individuals secreted higher levels of molecules such as interleukin-6 and RANKL after stimulation, pointing to a readiness to drive inflammation.
According to Dr. Singh, this finding confirms what researchers have suspected for some time.
“They showed that inflammation and immune changes are already happening before the final stage of joint pain. Once pain begins, we know clinical rheumatoid arthritis has set in. But this study shows changes even earlier—in that subclinical phase.”
Mohini Gray, a rheumatologist at the University of Edinburgh, said, “The data support the idea that immune cells are primed during the pre-arthritic period. RA often begins years before symptoms, so the findings aren’t surprising.”
However, Dr. Singh cautioned, “It’s hard to say if this priming is causal or just correlational. In genetically susceptible individuals, a citrullinated protein may be presented as foreign, triggering T and B cells. The study shows this: a rise in certain T and B cell populations.”
For the individuals who did go on to develop RA during the study, the immune system showed clear warning signs. A group of T cells that normally help coordinate immune responses began to grow in number. Instead of protecting the body, they seemed to encourage B cells to make harmful antibodies. The B cells themselves also changed, taking on unusual forms linked to long-term autoimmune activity. When arthritis symptoms finally appeared, another shift occurred: inflammatory cells called monocytes became very active, releasing powerful molecules like TNF and IL-1B. These changes spilled into the joints, driving the painful swelling and damage seen in RA.
The researchers also searched for genetic activity patterns to separate “converters” from “non-converters.” Only minor differences appeared, likely due to patient variability and the study’s limited size.
New avenues for intervention
One of the most clinically relevant findings was that the gene signatures observed in “converters” resembled the immune changes reversed by abatacept, a drug that blocks T cell co-stimulation. By contrast, they did not overlap with the effects of TNF inhibitors, which are standard treatments once RA is established.
The researchers suggest that early intervention targeting T cell activation, rather than late-stage inflammation, could delay or prevent disease onset.
“Abatacept, a CTLA4-Ig fusion protein, has already been tested in at-risk individuals,” said Dr. Singh. “These findings fit with that, adding to what we know, but don’t change clinical management yet.”
As multi-omic technologies continue to drop in cost, their use in early disease detection and prevention is becoming increasingly feasible. A similar strategy is already being applied in type 1 diabetes. In 2022, the FDA approved teplizumab, an anti-CD3 monoclonal antibody, as the treatment shown to delay the onset of type 1 diabetes in high-risk individuals. This success points to the possibility of applying comparable approaches in rheumatoid arthritis.
Beyond the specific findings, the researchers have made their dataset publicly available through an interactive online portal. This will allow other scientists to explore the detailed profiles of immune cells and plasma proteins at various stages of RA progression. The hope is that such resources can accelerate discovery not just for RA, but for other autoimmune conditions such as lupus, type 1 diabetes, and multiple sclerosis, where preclinical changes precede symptoms.
Manjeera Gowravaram has a PhD in RNA biochemistry and works as a freelance science writer.
