Mitogenicity of Corynebacterium parvum for mouse lymphocytes.

Corynebacterium parvum, a powerful in vivo immunostimulant, is shown to stimulate lymphocyte proliferation in vitro. C. parvum is mitogenic for B lymphocytes and does not stimulate T cells. The mitogenicity is dependent on the presence of macrophages. C. diphtheriae and another strain of C. parvum, both of which are devoid of adjuvant, RES stimulation, and tumour-inhibiting activities in vivo are nevertheless mitogenic. A lipid-free fraction from C. parvum, which retains in vivo immunostimulatory properties, is not mitogenic. Thus the mitogenic property is not correlated with the in vivo properties of C. parvum.