Tissue reaction after subcutaneous injection of Taenia saginata oncospheres

After subcutaneous injection of T. saginata oncospheres, a slight swelling is visible at the site of injection first after 13 days. Conspicuous projecting nodes appear after 3-4 weeks. Histological examinations of the site of injection revealed the following changes: On days 3 and 4 p.i.--edema, focal necrosis and haemorrhage, exudation of leukocytes, activation of monocytes and fibroblasts. On day 7 p.i.--in addition to edema and foci of eosinophiles, a striking activation of monocytes and fibroblasts, focal accumulation of macrophages, proliferation of blood capillaries and formation of collagen. On day 10 p.i.--eosinophiles and light macrophages around the larvae, fibroplastic granulation tissue at the periphery and collagenous connective tissue abundant. Hyperplasia of lymphoid tissue starts to appear at this time. On days 13-14 p.i.--a large amount of newly formed connective tissue in granulation tissue, diffuse infiltration of eosinophiles and hyperplasia of lymphatic tissue. On days 19-34 p.i.--haemorrhage around the cysticerci, activation of macrophages, phagocytizing erythrocytes. Endothelia of blood capillaries proliferate; lymphatic follicles are formed at the periphery of nodular affection which appears after inoculation of oncospheres. On day 34 p.i.--distinct formation of a pseudocyst. At the period from 53th to 61st day after injection, there is a mature collagenous connective tissue among the cysts, but still strongly infiltrated with cells. Clusters of siderophages are visible in connective tissue septa between the cysts.