Immunomodulation by myxospores of Myxococcus xanthus

Glycerol-induced myxospores of Myxococcus xanthus caused non-specific modulation of humoral and cellular immune responses in laboratory animals. The number of cells which formed specific haemolysins in spleens of mice immunized with sheep erythrocytes was increased when 0.5 X 10(8) myxospores were inoculated 2 d after the erythrocytes, and decreased when myxospores were injected 2 d before or at the same time as the erythrocytes. Both the IgG primary response and the secondary response to erythrocytes were decreased in rabbits after pretreatment with 2 X 10(8) myxospores per rabbit. Delayed-type hypersensitivity to sheep erythrocytes was also suppressed in mice after intraperitoneal (i.p.) injection of 0.3 X 10(8) myxospores. One day after i.p. injection of myxospores, neither an inflammatory response nor bone marrow cell depletion was observed in mice. These results support the idea that M. xanthus myxospores possess diverse immunomodulation properties apparently due to factors different from the classical LPS of Gram-negative bacteria.