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.