Figure 3. WT Tfh-like cells promote GC response in Sh2d1a^−/− mice.

GC B cells (B220⁺IgD^loGL7^hiFas^hi) in draining lymph nodes six days post-immunization with NP-OVA in Alum. (A) Left: WT or Sh2d1a^−/− mice without cell transfers; middle and right: transfer of WT or Sh2d1a^−/− in vitro generated Th2 or Tfh-like cells into Sh2d1a^−/− hosts one day prior to immunization. (B) Summary of % GC B cells in Sh2d1a^−/− mice after cell transfer and immunization. Immunized WT mice had an average of 14.35 +/− 0.65 SEM % GC B cells. Transferred cells: WT, filled circles; Sh2d1a^−/, open circles; no cells transferred (nt), open triangles. P<0.005 for WT Tfh-like cell transfers compared to all other cell transfers. (C) Tfh cells (CXCR5⁺PD-1⁺) in Sh2d1a^−/− mice after transfer of Tfh-like cells and immunization. Left: total Tfh cells (gated on CD4⁺CD44^hi); right: transferred donor cells (gated on CD4⁺CD44^hiGFP⁺). (D) Summary of % GFP⁺ cells, 6 days post-immunization in draining LNs of Sh2d1a^−/− mice that received WT or Sh2d1a^−/− Tfh-like cells. Data points represent one mouse, from three or more independent experiments. (E) Immunofluorescence of draining lymph node sections. Top Panel: GFP⁺ OT-II cells (GFP⁺, green); GC (PNA, red); follicle (IgD, blue), 6 days after immunization. Middle panel: IgD and GFP⁺ cells only. Lower panel: GFP staining alone for better visualization. (F) NP-specific antibody titers (total IgG, IgG₁, IgG_2b) measured by ELISA. Data in (A), (C) and (F) are representative of three or more independent experiments.