Stromal collapse in acute atrophy of lymphoid organs

The formation of post-collapse fibrosis was investigated in lymphoid tissues of rats simultaneously treated with cyclophosphamide and betamethazone. Effectiveness of treatment was monitored by means of peripheral blood smears. Animals were sacrificed 1, 2, 3, 4, and 7 days after the last injection. Fragments of lymph nodes and thymus were studied by light and electron microscopy. Compared with untreated controls, lymphoid organs from treated animals revealed considerable reduction in the number of cells and condensation of the stroma. Picrosirius-red stained slides seen under polarized light revealed the condensed stroma to contain mainly collagens. Electron microscopy confirmed the presence of collapsed collagen fibrils in the absence of signs of functional activation of the connective tissue cells within the collapsed areas. This investigation shows that a pure form of collapse fibrosis can be observed in lymph nodes and thymus following sudden atrophy of lymphoid cells.