INTRODUCTION: Controversial evidence points towards an expansion of the Th17 subset during the acute phase of the AAV, with a decline in remission. We hypothesize that the evaluation of the Th17 response to MPO or PR3 antigens may be useful to assess disease activity.
METHODS: We included 40 AAV patients (23 in stable remission and 17 in acute phase of the disease) and 5 healthy controls. We cultured PBMC for 48 hours under MPO or PR3 stimulation and measured Th17 responsiveness to these antigens using an ELISpot assay. We also determined IL-17 concentration in cell culture supernatants by ELISA and in serum. We registered clinical and analytical variables from medical records.
RESULTS: 5 patients from the remission cohort were excluded due to lack of response to polyclonal stimulus in the ELISpot test. Acute AAV patients showed higher Th17 response to MPO/PR3 stimulation evaluated by ELISpot compared to remission patients (p=0.025). Th17 response normalizes in the remission phase of the disease to levels present in healthy controls (p=0.9). In the same line, IL17 in the supernatant of PBMC cell culture was higher in acute patients than in remission patients (p=0.043), and we found no significant differences between remission and healthy controls. In contrary, Th17 response after antigen stimulation did not correlate with basal serum IL17 levels. Number of Spots/106 PBMC showed an AUC=0.82 (p=0.002) for the detection of disease activity, with a 64.7% sensitivity, 94% specificity and likelihood ratio=11 for a cutoff of 5 Spots/106 PBMC. In correlation with clinical parameters, remission patients with history of relapse showed higher Th17 response to MPO/PR3 (p=0.047). In addition, remission patients with persistence of hematuria also presented higher responsiveness compare to those without hematuria (p=0.012). We did not find significant differences with other parameters as ANCA titers, proteinuria, CPR or renal function.
CONCLUSIONS: Th17 response to MPO or PR3 measured by ELISpot or supernatant concentration of IL17 after PBMC cell culture are higher in acute phase in AAV patients. Higher ELISpot responses were noticed in patients who relapsed or who presented hematuria during the remission phase, as surrogate markers of higher disease activity.
Comments