Blastic Transformation of Mouse Spleen Lymphocytes by a Water-Soluble Mitogen Extracted from Nocardia

A water-soluble extract of Nocardia markedly increased in vitro [³H]thymidine incorporation by mouse spleen lymphocytes. The blastogenic activity of the extract and lipopolysaccharide was studied comparatively on various mouse lymphocyte subpopulations. The data obtained by [³H]thymidine incorporation and by electron microscopy have demonstrated that this preparation stimulates selectively mouse bone-marrow-derived cortisone-sensitive lymphocytes. This stimulation is related neither to a natural infection of mice with Nocardia organisms nor to the presence in Nocardia water-soluble mitogen of a lipopolysaccharide contaminant or of a lipopolysaccharide-like material.