Cellular depletion in Peyer's patches after cyclophosphamide treatment in mice.

The cytotoxic effects of cyclophosphamide (CY) in mice given by the intravenous route at the dose of 200 mg per kg of body weight, were investigated in Peyer's patches comparatively with peripheral blood and mesenteric lymph node as well as changes in the spleen weight. Peyer's patches are the sites of a more intense and durable cellular depletion than the mesenteric lymph node, observed as soon as day 1. A partial restauration of cell populations was observed from the 9th day, but even at day 21 their number remained lower than in control mice. Histological studies failed to show any germinal centre throughout the experiment; just a few cells were observed, 2 days after CY injection, in the interfollicular areas in which cells in mitosis were only seen at day 7. This preliminary results allow to study the role of the Peyer's patches as first barrier against penetration of an enteropathogenic bacteria able to invade the host tissues through the intestinal wall components after local or general acquired immunodeficiency.