Expansion of the innate immune system in mice with autoimmunity. Lethally irradiated Balb mice received transplants of TCD B6.SJL (CD45.1) BM plus 3 × 10⁵ B6.SJL spleen cells. Spleen cells were obtained from GVHD mice 3 to 4 weeks after BMT and transferred into either B6 (n = 6) or Balb (n = 6) Rag mice. Mice in each cohort were killed approximately 2 months after transfer and analyzed for spleen cellularity and absolute numbers of Gr-1⁺, Mac-1⁺, and CD11c⁺ cells (A) as well as the absolute numbers of Gr-1⁺, Mac-1⁺, and CD11c⁺ cells that were of donor (CD45.1) or host (CD45.2) origin (B). Data are cumulative results from 2 independent experiments. Histology of representative bone marrows from B6 (C) or Balb (D) Rag mice that received spleen cells from lethally irradiated Balb mice that had received transplants of TCD B6 BM plus B6 spleen cells to induce GVHD (original magnification, × 200). Marrow from B6 Rag mouse shows an almost homogenous population of mature neutrophils, while marrow from Balb Rag mouse demonstrates a heterogenous population of erythroid, myeloid, and megakaryocytic cells. In panels A and B, error bars indicate standard error measurement (SEM).