Oral administration of polymyxin B ameliorated GVHD. Lethally irradiated B6D2F1 mice were transplanted with 5 × 106 TCD BM without or with 2 × 106 T cells from B6 or B6-Ly5.1 (CD45.1+) donors. Polymyxin B (PMB; 100 mg/kg) or diluent was administered by daily oral gavage from day −4 until day 28 after BMT. (A) Fecal pellets were collected once per week after BMT and intestinal microflora was characterized by RFLP analysis of 16S rRNA genes constructed from each sample of fecal pellets and digested with HhaI. Representative RFLP patterns are shown in mice with GVHD receiving diluent (a-e) and those with PMB (f-j) 7 days after BMT. Arrows indicate an OTU for E coli. (B) Time course changes in the proportion of E coli (n = 6-12 / group). Survival (C) and clinical GVHD scores (D, mean ± SE) after BMT are shown (n = 6-12/group). Data from 2 independent experiments were combined. (E) Numbers of donor (CD45.1+) T cells in mLNs on day 5 (n = 20/group). (F) Pathology scores of the small intestine on day 7 (n = 20/group). Data from 3 independent experiments were combined and are shown as mean ± SE (*P < .05).
