Fig. 4

Phenotypic and functional analysis of antibody-secreting cells during acute phase of SFTS. a FACS gating strategy to define plasmablasts and memory B cells by CD27 and CD38, as well as immunoglobulin staining of PBs and MBs. b Kinetics of the numbers of PBs (upper left panel) and MBs (lower left panel), and phenotypic analysis of immunoglobulin class-switching response of ASCs of survived and deceased group. IgM⁺IgG⁻ and IgG⁺IgM⁻ subsets represent the class-unswitched (right panels) and class-switched (middle panels) ASCs, respectively. Black triangles, red circles and blue horizontal lines represent means of survived, deceased and HC group respectively. Statistic analysis was conducted between the survived and deceased groups. *p < 0.05, **p < 0.005. c FACS gating strategy defining IgA and IgD expression in CD27⁺CD38⁺ subset of B cells. d The ratio of IgA⁺ or IgD⁺ cells in CD27⁺CD38⁺ subset of B cells among the deceased, survived patients and healthy donors (HC), shown as means ± SD. e, f Expression levels of transcription factors BLIMP-1, IRF-4 and XBP-1 were determined in the CD27⁺CD38⁺ subset of B cells from patients or healthy donors (HC) as shown in heatmap (e) or bargraph (f). Statistic analysis was conducted by t test. *p < 0.05, **p < 0.005, NS = no significance. g ELISPOT analysis for the detection of Gn-specific ASCs of three representative patients (two survivors and one deceased). The fresh peripheral blood samples of three patients (P28, P29, and P30) were collected at day 5, 14, and 10 post symptom onset, respectively. The ELISpot analysis was performed as described in the Methods section. The survived patients (P28 and P29) showed positive Gn-specific response as compared with corresponding negative control, and the deceased patient (P30) showed negative result. Error bar represents the standard deviation