The dominant theory about vaccines that include a capsular polysaccharide is that they stimulate the immune system to make antibodies that will target the pathogen for “opsonic killing” – busting it open using phagocytes. But we now know that there are human antibodies specific to capsular polysaccharides that protect us against pneumococcus but do not promote opsonic killing. How do they protect us if they don’t activate the body to destroy the pathogen?
In the mBio study, Yano et al. looked closely at the possible connections between one non-opsonic antibody and quorum sensing and found that it increases the rate at which the bacteria share DNA. This enhanced cell-cell communication, which triggered quorum sensing and “fratricide”, the production of bacteriocins that kill the bacterium’s own “brother” cells.
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