IgA-dependent, monocyte-mediated, antibacterial activity

IgA purified from the sera of patients convalescing from disseminated group C meningococcal disease induced human monocyte-mediated anti- meningococcal activity in vitro in the absence of complement. Both IgA- and IgG-dependent activity were directed against the group C meningococcal polysaccharide (Csss) capsule. The amount of IgA that was effective bound less than 1 ng of Csss. Antibacterial activity was dependent upon the length and the temperature of the test incubation and on the concentration of monocytes. The implications of this mechanism for local cell-mediated antibacterial immunity are discussed.