Relationship of Clearance and Deposition of Silica to Histological and Immunological Changes

摘要

Inbred female Balb/c-mice were exposed to silica (7631869) dust over a period of 39 weeks to study alterations of B-lymphocyte immunocompetence. At all time points following the aerosol stimulation of the mice with whole Escherichia-coli-055:B5, the thymus independent anti Escherichia-coli lipopolysaccharide (LPS) response was significantly suppressed in the spleen. In the mediastinal lymph nodes (MLN) the immune response to LPS was enhanced at 9 weeks, followed by a depression. When the silicon damaged lungs were bypassed using an intravenous injection of the antigen the response was not noted. Histological examination of silicotic lesions indicated silica laden aggregations or dust cells at 24, 33, 36, and 39 weeks. The presence of silica dust in the lungs was confirmed using energy dispersive x-ray analysis, which also identified submicroscopic silica particles in the spleen. The lungs and MLNs demonstrated granulomatous and fibrotic changes at 39 weeks. Aerosol immunized lungs demonstrated perivascular and peribronchiolar lymphocytic cuffing. The bronchioles of silica exposed animals contained a greater number of macrophages. Infiltration of macrophages was noted adjacent to blood vessels and respiratory airways on scanning electron microscopy examination.