Changed expression of leukocyte adhesion molecules and increased production of reactive oxygen species caused by Streptococcus pyogenes in human whole blood

To elucidate the innate immune responses to group A streptococci (GAS) impo rtant in the pathophysiology of sepsis, now cytometric techniques were appl ied to study the effects of live and heat-inactivated GAS, including their particulate and soluble components, on the expression of leukocyte adhesion molecules CD11b (Mac-l) and CD62L (L-selectin), and leukocyte production o f reactive oxygen species (ROS in human whole blood. GAS caused marked time - and concentration-dependent increases in CD11b and ROS, while CD62L was d ownregulated. Live and heat-inactivated GAS induced similar changes in leuk ocyte adhesion molecules, whereas ROS production induced by heat-inactivate d GAS land its particulate fraction) was 4 (2.5)-fold higher than with live GAS. Leukocyte nitric oxide production (24 h) was not enhanced. Although G AS proved a more potent inducer of ROS production, leukocyte responses to G AS were similar to those reported for lipolysaccharides, indicating that Gr am-positive and Cram-negative bacteria activate common pathways in the infl ammatory response. Nigh ROS production may contribute to tissue damage caus ed by GAS.