52 The pathogenic relevance of t follicular helper cells-plasmablasts axis in patients with systemic lupus erythematosus

Background and aims The aim of this study was to assess the peripheral immune cell phenotypes in a correlation with clinical findings in patients with systemic lupus erythematosus (SLE). Methods Peripheral blood mononuclear cells were obtained from 143 SLE patients and 26 healthy donors (HD). Circulating B, T and dendritic cells were defined based on flow cytometric analysis for human immune system termed “the Human Immunology Project” proposed by the National Institutes of Health (NIH) and the Federation of Clinical Immunology Societies (FOCIS). Results The proportions of CD3 + CD4 + CXCR5 + ICOS + T follicular helper (Tfh) cells, but not CD3 + CD4 + CXCR3 + CCR6 - Th1 and CD3 + CD4 + CXCR3 - CCR6 + Th17 cells, were higher in SLE than the HD. The proportions of CD19 + CD20 + IgD + CD27 + central memory B cells and CD19 + CD20 + IgD - CD27 - effector B cells were higher in SLE. The largest difference relative to the HD was observed in the proportion of CD19 + CD20 - CD27 + CD38 + plasmablasts, which was higher in SLE and correlated with BILAG index. The proportion of Tfh cells correlated with serum IgG level, and the proportion of activated Tfh cells correlated with serum anti-Sm antibody level. Among helper T cell subsets (Th1, Th17, Treg and Tfh), Tfh cells only showed positive correlation with the proportion of plasmablast (r=0.24, p=0.02). Conclusions Peripheral immuno-phenotyping confirmed the importance of Tfh-plasmablasts axis in patients with SLE, i.e. activation of Tfh cells correlated with autoantibody production while plasmablast did with disease activity of SLE. Our findings supported the relevance of Tfh-plasmablasts axis as a potential therapeutic target for SLE.