Figure 8. Host microglial cells are increased during graft-versus-host disease (GVHD) and regulated by IL-6.

(A) Immunostain of F4/80 expression in the prefrontal cortex from BALB/c mice transplanted with bone marrow (BM) alone or together with B6 spleen cells (adjusted to a dose of 0.6 × 10⁶ αβ T cells) (GVHD). Brown staining denotes F4/80⁺ cells. Original magnification is ×200. (B) F4/80 expression on host (H-2K^d+) cells from animals transplanted with BM alone or BM and spleen cells (GVHD) 11–12 days after transplantation. Isotype control antibody is shown for comparison. (C) Total number of F4/80⁺ cells in the brain of BM control (●, n = 10) or GVHD mice (■, n = 9). (D) Dot plot depicting CD45.2^loCD11b⁺ microglial and CD45.2^hiCD11b⁺ macrophages in the brain from GVHD animals. (E) Total number of microglia and macrophages in the brains from BM control or GVHD animals on day 14. (F) Representative histogram depicting intracellular IDO expression in CD45.2^loCD11b⁺ microglial cells derived from BM or GVHD mice. (G) Nos2, Arg1, and Ym1 mRNA expression in the brains of BALB/c mice transplanted with B6 BM alone (●, n = 9) or B6 BM and spleen cells (adjusted to a dose of 0.6 × 10⁶ αβ T cells) (■, n = 9) 14 days after transplantation. (H) Nos2, Arg1, and Ym1 mRNA expression in the brains of B6 mice reconstituted with B10.BR BM alone (●, n = 5) or with B10.BR spleen cells (adjusted to a dose of 4.5 × 10⁶ αβ T cells) (■, n = 9). (I) The absolute number of CD45.2^loCD11b⁺ microglial cells in the brains of BALB/c mice transplanted with B6 BM alone (●, n = 6) or together with B6 spleen cells on day 14. Mice transplanted with B6 BM and spleen cells were treated with either an isotype control (■, n = 10) or anti–IL-6 receptor (α–IL-6R) antibody on days 0 and 7 (▲, n = 10). Data are from 2 experiments in all panels. Statistically significant differences were calculated using the 2-tailed Mann-Whitney U test. *P < 0.05, **P < 0.01, ***P < 0.001.