Influence of RU 41.740, a glycoprotein extract from Klebsiella pneumoniae, on the murine immune system. I. T-independent polyclonal B cell activation.

A glycoprotein extract from Klebsiella pneumoniae, RU 41.740, has been shown clinically to reduce infectious episodes in patients prone to frequent infections, and experimentally to reduce mortality in animals infected with various bacteria or viruses. The method of action of RU 41.740 in conferring protection from infection is as yet unknown, but in experimental animals, RU 41.740 appears to influence B and T cells as well as macrophages. We report here that RU 41.740 is a strong polyclonal B cell activator and that it activates B cells in a T-independent manner. RU 41.740 also activates spleen cells from the LPS-nonresponder mouse strains, C3H/HeJ and C57BL/10ScCr, which indicates that the polyclonal B cell activating ability of RU 41.740 is not due to contamination by LPS.