Mycobacterium paratuberculosis causes a chronic granulomatous enteritis in adult sheep. The lamina propria intestinal macrophage appears to be pivotal in the pathogenesis of this disease. The granulomatous pathology and wasting seen in clinical Johne's disease is consistent with certain biological activities of the monokines TNF-alpha and IL-1. The purpose of this study was firstly to compare the phenotype of intestinal lamina propria macrophages from healthy control sheep and diseased animals. Secondly to compare the levels of cytokines provided by lamina propria cells from control and disease sheep. Lamina propria cells were isolated from gut tissue and phenotyped using FACS and immunohistochemistry. Preliminary results show increased numbers of VPM 65 (ovine macrophage monoclonal antibody) - reactive cells in diseased gut. However cell surface expression of this and some other markers examined appears not to be significantly altered. Cytokine message levels were determined by PCR on intestinal mucosa using oligonucleotide primers specific for ovine TNF-alpha and LI-1. Preliminary results from agarose gel analysis show increased signals for both cytokines in diseased compared with control tissue. Increased levels of TNF-alpha and IL-1 NRNA in the lamina propria suggest that these cytokines may be important mediators in the pathogenesis of paratuberculosis. Further studies to localize cytokine production are in progress.