Characteristics and prognostic implications of peripheral blood lymphocyte subsets in patients with anti-MDA5 antibody positive dermatomyositis-interstitial lung disease

Objectives To examine the characteristics of blood lymphocyte subsets in dermatomyositis-interstitial lung disease (DM-ILD) inflicted patients with positive anti-melanoma differentiation-associated gene 5 (anti-MDA5), as well as its prognosis value in this set of patients. Methods Data were retrospectively collected from 253 DM-ILD patients from three hospitals in China between January 2016 to January 2021. Patients were grouped into anti-MDA5 antibody positive group (MDA5.sup.+ DM-ILD) and anti-MDA5 antibody negative group (MDA5.sup.- DM-ILD) based on myositis-specific autoantibody test results. Demographic characteristics, lymphocyte subsets patterns and other clinical features were compared between the two groups. The association of lymphocyte subsets with 180-day mortality was investigated using survival analysis in MDA5.sup.+ DM-ILD. Results Out of 253 eligible patients with DM-ILD, 59 patients were anti-MDA5.sup.+ and 194 were anti-MDA5.sup.-. Peripheral blood lymphocyte count, CD3.sup.+ count, percentage of CD3.sup.+, CD3.sup.+CD4.sup.+ count, and CD3.sup.+CD8.sup.+ count was lower in MDA5.sup.+ DM-ILD than in MDA5.sup.- DM-ILD.sup.- (all P < 0.001) as well as CD3.sup.-CD19.sup.+ count (P = 0.04). In MDA5.sup.+ DM-ILD, CD3.sup.+CD8.sup.+ count [less than or equal to] 49.22 cell/[mu]L (HR = 3.81, 95%CI [1.20,12.14]) and CD3-CD19.sup.+ count [less than or equal to] 137.64 cell/[mu]L (HR = 3.43, 95%CI [1.15,10.24]) were independent predictors of mortality. CD3.sup.+CD8.sup.+ count [less than or equal to] 31.38 cell/[mu]L was associated with a higher mortality risk in all DM-ILD patients (HR = 8.6, 95%CI [2.12,31.44]) after adjusting for anti-MDA5 and other clinical characteristics. Conclusion Significant lymphocytes decrease was observed in MDA5.sup.+ DM-ILD patients. CD3.sup.+CD8.sup.+ cell count was associated with worse prognosis in both MDA5.sup.+ DM-ILD and all DM-ILD patients. Keywords: Anti-melanoma differentiation-associated gene 5, Dermatomyositis, Interstitial lung disease, Lymphocyte subsets, Prognostic