The effects of neonatal thymectomy on the antitumour activity of lentinan, carboxymethylpachymaran and zymosan, and their effects on various immune responses

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Abstract
The mechanism of antitumour action of the polysaccharides, lentinan and carboxymethylpachymaran, was examined and compared with that of zymosan. It was revealed that (1) these polysaccharides did not show any direct cytocidal effect on tumour cells; (2) these polysaccharides had no antitumour action at all in neonatally thymectomized mice, indicating the important role of the thymus gland in tumour regression; and (3) in spite of these facts, these polysaccharides, contrary to zymosan, did not accelerate various conventional immune responses such as phagocytic activity, antibody production against heterologous antigen, increased number of peripheral lymphocytes, skin homograft rejection, and delayed hypersensitivity. This evidence suggests the presence of a complex and unknown mechanism for regression of transplanted tumour in the action of lentinan and carboxymethylpachymaran.