MyD88-dependent influx of monocytes and neutrophils impairs lymph node B cell responses to chikungunya virus infection via Irf5, Nos2 and Nox2

McCarthy, Mary K.; Reynoso, Glennys V.; Winkler, Emma S.; Mack, Matthias; Diamond, Michael S.; Hickman, Heather D.; Morrison, Thomas E.

Pathogenic CHIKV infection causes marked disorganization of lymphocyte populations within the dLN [23] , with paracortical relocalization of B cells, diffuse positioning of CD8 + T cells, and loss of a well-defined B-T cell border by 5 dpi. In mice treated with anti-Gr-1 mAb prior to pathogenic CHIKV infection, we observed improved follicular organization and a defined B-T cell border compared with the isotype control group (Fig 2K) . Together, these data suggest that the early influx of monocytes and neutrophils into the dLN following Delaying the early influx of myeloid cells to the dLN prevents lymphocyte depletion and restores dLN architecture. C57BL/6 mice were left untreated or treated with 300-500 μg of IgG2b isotype control mAb or anti-Gr-1 mAb via intraperitoneal injection one day prior to inoculation with 10 3 PFU of CHIKV 181/25 or AF15561 in the left footpad. (A) Representative flow cytometry plots and percentages of (B) CD11b + Ly6C hi monocytes or (C) CD11b hi Ly6C + Ly6G + neutrophils in the blood. (D) Representative flow cytometry plots and numbers of (E) CD11b + Ly6C hi monocytes or (F) CD11b hi Ly6C + Ly6G + neutrophils in the dLN. Data are combined from two independent experiments (n = 3 (mock) to 7 per group). At 5 dpi, the dLN was analyzed for (G) total cells, (H) CD19 + B220 + B cells, (I) TCRβ + CD4 + T cells, and (J) TCRβ + CD8 + T cells. Data are combined from 3 independent experiments (n = 4 (mock) or 11 per group). (K) Frozen dLN sections were stained for ERTR7 + stromal cells (red), B220 + B cells (blue), or CD8 + T cells (green). Errors bars represent mean ± SEM. Data in (G-J) are pathogenic CHIKV infection results in both impaired lymphocyte accumulation and altered lymphocyte localization.