THYMIC EXTRACELLULAR-MATRIX IN HUMAN MALNUTRITION

Previous studies have shown that malnutrition severely affects both ly mphoid and epithelial components of the thymus. Yet, few data are avai lable concerning the extracellular matrix (ECM) of the thymic microenv ironment in malnutrition. We studied by histological, ultrastructural, and immunohistochemical means thymuses obtained in necropsies from 19 malnourished children. We observed a consistent increase in the intra lobular ECM-containing network which could be ascertained histological ly by the dense reticulin staining. This abnormally dense ECM network contained fibronectin, laminin, and type IV collagen. Importantly, the enhancement of thymic ECM in malnourished individuals positively corr elated with the degree of thymocyte depletion. This correlation may re present a cause-effect relationship in which the contact of thymocytes with abnormally high amounts of thymic ECM triggers and/or enhances p rogrammed cell death.