DEVELOPED AND RESOLVING LESIONS IN PORCINE PROLIFERATIVE ENTEROPATHY - POSSIBLE PATHOGENETIC MECHANISMS

Proliferative enteropathy, caused by Lawsonia intracellularis, offers the opportunity to examine bacterial mechanisms that influence epithel ial cell proliferation. Ultrastructural features of developed and reso lving lesions included the presence of enlarged intestinal crypts cont aining undifferentiated immature epithelial cells and an absence of go blet cells. Numerous intracytoplasmic bacteria, identified as L. intra cellularis, were consistently present within affected cells. In recove ring intestinal tissue. additional features were (1) the common presen ce of pale, swollen;; protruding epithelial cells, (2) shrunken, degen erate epithelial cells, (3) apoptotic bodies in both epithelial cells and macrophages, (4) the reappearance of normal goblet cells, and (5) reduced numbers of L. intracellularis within lesions. Bacteria were re leased from cells via cytoplasmic and cellular protrusions into the in testinal lumen. It is speculated that the presence of the intracytopla smic bacterium, L. intracellularis, may disrupt normal processes of ce ll growth, differentiation or apoptosis in the intestinal epithelium. (C) 1996 W.B. Saunders Company Limited