Active episodes of the inflammatory bowel diseases (IBD) are associated with the infiltration of large numbers of myeloid cells including neutrophils, monocytes and macrophages. The objective of this study was to systematically characterize and define the different populations of myeloid cells generated in a mouse model of chronic gut inflammation. Using the T cell transfer model of chronic colitis, we found that induction of disease was associated with enhanced production of myelopoietic cytokines (IL-17, G-CSF), increased production of neutrophils and monocytes and infiltration of large numbers of myeloid cells into the MLNs and colon. Detailed characterization of these myeloid cells revealed three major populations including Mac-1+Ly6ChighGr-1low/neg cells (monocytes), Mac-1+Ly6CintGr-1+ cells (neutrophils) and Mac-1+Ly6Clow/negGr-1low/neg leukocytes (macrophages, dendritic cells, and eosinophils). In addition, we observed enhanced surface expression of MHC class II and CD86 on neutrophils isolated from the inflamed colon when compared to neutrophils obtained from the blood, MLNs and spleen of colitic mice. Furthermore, we found that colonic neutrophils had acquired antigen-presenting cell (APC) function that enabled these granulocytes to induce proliferation of ovalbumin-specific CD4+ T cells in an antigen- and MHC class II-dependent manner. Finally, we observed a synergistic increase in pro-inflammatory cytokine and chemokine production following co-culture of T cells with neutrophils in vitro. Taken together, our data suggest that extravasated neutrophils acquire APC function within the inflamed bowel where they may perpetuate chronic gut inflammation by inducing T cell activation and proliferation as well as by enhancing production of pro-inflammatory mediators.