Context dependent induction of autoimmunity by TNF signaling deficiency

Circulating Tfh cells are differentially modified by abatacept or TNF blockers and predict treatment response in rheumatoid arthritis

OBJECTIVE

CD4+CXCR5+PD-1hi follicular helper T (Tfh) cells dwell in the germinal centres (GCs) of lymphoid organs and participate in RA pathogenesis. The frequency of their circulating counterparts (cTfh frequency) is expanded in RA and correlates with the pool of GC Tfh cells. Our objective was to study the effect of abatacept (ABT) or TNF blockers (TNFbs) on the cTfh frequency in RA.

METHODS

Peripheral blood was drawn from seropositive, long-standing RA patients chronically receiving conventional synthetic DMARDs (csDMARDs; n = 45), TNFb (n = 59) or ABT (n = 34) and healthy controls (HCs; n = 137). Also, patients with an incomplete response to csDMARDs (n = 41) who initiated TNFb (n = 19) or ABT (n = 22) were studied at 0 and 12 months. The cTfh frequency was examined by cytometry.

RESULTS

As compared with HCs, an increased cTfh frequency was seen in seropositive, long-standing RA patients chronically receiving csDMARDs or TNFb but not ABT. After changing from csDMARDs, the cTfh frequency did not vary in patients who were given TNFb but decreased to HC levels in those given ABT. In the ABT group, the baseline cTfh frequency was higher for patients who attained 12-month remission (12mr) vs those who remained active (12ma): 0 month cut-off for remission >0.38% [sensitivity 92%, specificity 90%, odds ratio (OR) 25.3]. Conversely, in the TNFb group, the baseline cTfh frequency was lower for 12mr vs 12ma: 0 month cut-off for non-remission >0.44% (sensitivity 67%, specificity 90%, OR 8.5).

CONCLUSION

ABT but not TNFb was able to curtail the cTfh frequency in RA. A higher baseline cTfh frequency predicts a good response to ABT but a poor response to TNFb.

Responses to Ang II (Angiotensin II), Salt Intake, and Lipopolysaccharide Reveal the Diverse Actions of TNF-α (Tumor Necrosis Factor-α) on Blood Pressure and Renal Function

TNF-α (tumor necrosis factor-alpha) is the best known as a proinflammatory cytokine; yet, this cytokine also has important immunomodulatory and regulatory functions. As the effects of TNF-α on immune system function were being revealed, the spectrum of its activities appeared in conflict with each other before investigators defined the settings and mechanisms by which TNF-α contributed to both host defense and chronic inflammation. These effects reflect self-protective mechanisms that may become harmful when dysregulated. The paradigm of physiological and pathophysiological effects of TNF-α has since been uncovered in the lung, colon, and kidney where its role has been identified in pulmonary edema, electrolyte reabsorption, and blood pressure regulation, respectively. Recent studies on the prohypertensive and inflammatory effects of TNF-α in the cardiovascular system juxtaposed to those related to NaCl and blood pressure homeostasis, the response of the kidney to lipopolysaccharide, and protection against bacterial infections are helping define the mechanisms by which TNF-α modulates distinct functions within the kidney. This review discusses how production of TNF-α by renal epithelial cells may contribute to regulatory mechanisms that not only govern electrolyte excretion and blood pressure homeostasis but also maintain the appropriate local hypersalinity environment needed for optimizing the innate immune response to bacterial infections in the kidney. It is possible that the wide range of effects mediated by TNF-α may be related to severity of disease, amount of inflammation and TNF-α levels, and the specific cell types that produce this cytokine, areas that remain to be investigated further.