Expression and function of IL-4 within FL cell niches. (A) IL4 was quantified by RT-qPCR in frozen tonsil (n = 5) and FL-LN (n = 12) sections. (B) IL4 was quantified by RT-qPCR in whole BM cells from HDs (n = 5) and FL patients (n = 20). (C) (i-ii) Immunohistochemical staining for CXCL12 and pSTAT6 on reactive tonsil, (iii-iv) FL LN with high CXCL12/pSTAT6 expression, and (v-vi) FL LN with low CXCL12/pSTAT6 expression. Original magnification ×100 (i-ii: scale bars, 100 μm), ×200 (iii-vi: scale bars, 50 μm). (D) Semiquantitative assessment of CXCL12 and pSTAT6 on FL tissue biopsies arranged on tissue microarray (TMA). CXCL12 was scored positive when the expression was higher than in reactive GCs, and pSTAT6 was scored positive when frequent nuclear-positive cells within the malignant follicles were observed. (E) Correlation between IL4 and CXCL12 expression across the 20 FL BM samples. ****P < .0001; *P < .05.