Transfer of 7 × 107 donor B6 splenocytes, depleted of CD25+ cells to eliminate endogenous Treg-cell activity, into CB6F1 recipients resulted in lethal aGVHD

in approximately 50% of mice within 25 ± 10 days (Fig. 1A). Acute disease was due to the high precursor F1 reactive cytotoxic lymphocyte frequency within donor inoculums, and also due to removal of Treg-cell activity [30, 31]. Therefore to develop a cGVHD model, B6 splenocytes were also depleted of CD8+ T cells, which resulted in no weight loss or lethality over the experimental duration (Fig. 1A), and animals surviving for greater than 15 weeks. In addition to hair loss (data BMS-354825 clinical trial not shown), analysis of peripheral blood and splenocytes showed consistent and long-term donor cell engraftment over 7 INK 128 order weeks following GVHD induction (Fig. 1B). Detected splenomegaly in cGVHD animals (Fig. 1C) was a consequence of both donor cell engraftment (Fig. 1D) and hyperproliferation of recipient lymphocyte compartments (Fig. 1E). Donor cells composed on average 7.0% (range 0.72–17.8%) of total splenocytes, and consisted predominantly of donor CD4+ T lymphocytes (3.4 ± 1.2%) with lower levels of B220+ B cells (0.63 ±

0.59%) (Fig. 1D). Of particular relevance to this disease model, donor cell transfer also resulted in an increase in the proportion of recipient splenic CD4+ T cells (cGVHD versus PBS, p = 0.004) and B cells (cGVHD versus PBS p = 0.02) (Fig. 1E). This was due to expansion of recipient

lymphocytes as evidenced by a mean 3.2- ± 1.1-fold increase in absolute numbers of recipient cells isolated from cGVHD spleens compared with those in sham-treated mice (Table 1), and lymphocyte hyperactivity as detected upon ex vivo re-stimulation (Fig. 1F). No differences in splenic composition of recipient CD3+CD4− T cells were detected (not shown). Donor engraftment and Rebamipide recipient hyperproliferation correlated with elevated serum IgG1 and IgG2a anti-single-stranded DNA autoantibodies and IgG immune complex deposition within kidney glomeruli (Fig. 1G and H). In concordance with previous reports [13], donor-derived B cells were not the main drivers of glomerulonephropathy as evidenced by maintenance of elevated serum autoantibody levels when using donor inoculates pre-depleted of B cells for cGVHD induction (Fig. 1G). Thus transfer of naïve B6 donor T cells induced an alloreactive response against recipient H-2d alloantigens presented via the direct and indirect pathways of alloantigen presentation, both of which are constitutively active within this model (Fig. 1I), resulting in autoimmune cGVHD pathology. Detection of IgG class switched antibodies indicated a T-cell dependent mechanism of B-cell activation was predominant.