Comparative studies on the ultrastructure of the rat lungs after intratumor treatment of Morris hepatoma with rhTNF-alpha and its muteins

The aim of the present study was the comparative analysis of morphological changes found in the lungs of Buffalo rats in the course of Morris hepatoma 5123 after i.t. treatment with recombinant human TNF-alpha (rhTNF-alpha) a nd its muteins. Modification of the native TNF-alpha molecule and synthesis of mutagenized analogues can prevent undesirable symptoms observed in the case of therapeutic administration of rhTNF-alpha. TNF-a has been shown to interact with two distinct membrane receptors (TNF-R): p55R and p75R. Mutag enized mutein V binds selectively with p55R. Mutein VI fails to recognize e ither TNF-R. The cytokines were applied in a dose of 10 mu g protein in a c ycle of 8 days. The control group consisted of tumor-bearing animals which were given PBS. Ultrastructural examinations were based on transmission ele ctron microscope (TEM). Mutein VT-receiving animals showed enhanced changes of cytotoxic nature. Severe damage to endothelial cells (necrosis inclusiv e) was observed. Blood vascular lumen showed accumulation of neutrophils an d monocytes. Features of enhanced activity of endothelial cells were noted. Focally, within pulmonary alveoli conglomerates of fibrin and fragments of damaged cells were found, with erythrocytes, neutrophils and macrophages i n their vicinity The epithelium of pulmonary alveoli showed signs of consid erable damage, including necrosis. The lumen of pulmonary capillaries in rh TNF-alpha-treated animals showed a predominance of eosinophils and monocyti c cells. Features of endothelial stimulation were observed, although withou t a tendency to form microthrombi. Much less pronounced changes both in the lung capillary bed and in the alveolar epithelial cells were noted in the mutein V-given animals. Our findings confirm the possibility of peripheral activation of cells involved in the cytokine-induced antitumor response. Mu tein V with the smallest effect on the lung tissue rebuilding seems to be a rhTNF-alpha derivative which can delimit the undesirable symptoms in the c ourse of antitumor therapy reduced to i.t. injections.