The inflammatory infiltrate in the acute stage of the dextran sulphate sodium induced colitis: B cell response differs depending on the percentage of DSS used to induce it

Background: Experimental colitis with features similar to inflammatory bowel disease (IBD) has initially been described. A detailed analysis of inflammatory cells has not yet been described. Therefore in this study we characterized the cells involved in the acute phase of the colitis and compared those findings to what is known about human IBD. Methods: Colitis was induced in BALB/C and C57B16 mice by ingestion of 2.5% and 5% DSS in the drinking water for 8 days. Cells were labelled by immunohistochemical staining with F4/80 and ER-MP20 for macrophages, TIB 120 for MHC Class II presentation, and anti-CD4 and anti-CD8 antibodies. They were enumerated by using a novel method that employs video image analysis. Immunoglobulin-producing cells were enumerated by immunofluorescent staining for IgA, IgG and IgM and counting by using confocal microscopy. Results: Inflammatory infiltrate in the acute phase of the dextran sulphate sodium (DSS)-induced colitis consists predominantly of macrophages, neutrophils and eosinophils. Neutrophils increase in numbers and crypt abscesses were also seen. Increased macrophage numbers were due to recently recruited monocytes from the peripheral circulation. It does not appear that there are any changes in T cell numbers or distribution. The inflammation induced changes in immunoglobulin-producing cells with IgA-producing cells affected the most. Conclusions: The effect on Ig-producing cells depends on the percentage of DSS used to induce colitis. In general, 2.5% DSS induces an increase and 5% DSS a depletion of these cells.