Fig 1: DOCK8+ CD4 T cell as T fh cell located at splenic red pulp, and its increase in peripheral blood of patients with SLE(A) a: Morphology of DOCK8+CD4 T cell observed by immunoelectron microscopy, stained with rabbit anti-DOCK8 Ab and Au-tagged ant-rabbit IgG Ab. (bar = 1µm; original magnification ×12,000). b,c: Nuclear membrane portions of DOCK8+ CD4 T cell, stained likewise. (bar = 1µm; original magnification ×18,000; x24,000).(B) Markers of splenic DOCK8+CD4 T cells. Flow cytometry for ICOS, CXCR5, and PD-1 expression in splenic DOCK8+CD4 T cells taken 9 days after the final immunization of BALB/c mice immunized 12x with PBS versus OVA (Left). Flow cytometry analysis of ICOS, CXCR5, PD-1, GATA3, ROR?t, T-bet, Bcl6, Ly6C, LFA1, FR4, and GL7 expression in splenic DOCK8-CD4 T cells and DOCK8+CD4 T cells isolated from 12x OVA-immunized BALB/c mice.(C) Cytokines released in culture supernatants of 1x106/ml DOCK8+ or DOCK8- CD4 T cells following incubation with 2 µg/mL of anti-CD3 and 5 µg/mL of anti-CD28 Ab at 37°C for 24hr. Data were represented as mean ± SEM. Statistical assessment was by Student's t-test. *p<0.05, **p<0.01, ***p<0.005, ****p<0.001.(D) DOCK8+CD4 T cells in the autopsied spleen of untreated patient with active SLE who died before starting therapy. Tissues were fixed in 10% formalin, deparaffinized by graded xylene, and graded alcohol sequentially, and serially treated with biotinylated anti-DOCK8 monoclonal Ab and rabbit anti-IFN? Ab (for T cell staining), alkaline phosphatase avidin D, and anti-rabbit Novolink, followed by reaction with Fast Red (Red for DOCK8+ cells) and Histogreen (Blue for T cells). S: red pulp sinus. A; central artery. P: penicillar artery. (bar = 100µm; original magnification ×100). Inset; Magnified DOCK8+CD4 T cells (Arrows). (bar = 20µm; original magnification ×400).(E) Circulating DOCK8+CD4 T cells within CD4 T cells in the peripheral blood of patients with SLE and its relationship to the SLE disease activity index (SLEDAI). Data of control patients were depicted as; ¦ rheumatoid arthritis, ? mixed connective tissue disease, ? polymyositis, ? systemic sclerosis, ? microscopic polyangiitis. Also shown was quantification of interferona (IFNa) in sera of the same patients with SLE measured by ELISA.See also Figures S2 and S4–S6.