Involvement of luminal bacteria, heat shock protein 60, macrophages and gamma delta T cells in dextran sulfate sodium-induced colitis in rats

The in vivo immunological events in dextran sulfate sodium (DSS) -induced c olitis were evaluated. Rats were fed water (control) or 5% DSS. Colonic sec tions were assessed by light microscopy, Gram stain, immunohistochemistry, and electron microscopy, A progressive decline in number and increase in fr agmentation of bacteria in the colonic lumen was observed over time. Lumina l bacteria were the first to show heat shock protein 60 (HSP60) staining (d ay 3), Macrophages in close proximity to these bacteria were next to show s uch staining (day 6), and finally the damaged epithelial cells when colitis became severe (day 15), Ultrastructural assessment showed cell-cell contac t interactions between macrophages and dendritic gamma delta T cells. An in crease in the number of ya T cells and ED1-positive macrophages in the affe cted colonic tissue over time was documented. These results suggest colonic bacteria, host macrophages, and gamma delta T cells play specific roles in the immunological reactions in DSS-induced colitis, possibly via an HSP60- mediated mechanism.