Detection and localization of a lectin on Actinomyces viscosus T14V by monoclonal antibodies.

A cell-associated lectin activity that mediates lactose-inhibitable adherence of Actinomyces viscosus T14V has been localized to a specific population of fimbriae by the use of monoclonal antibodies. Nine monoclonal antibodies were produced that reacted with only 1 of 2 immunoelectrophoretically distinct fimbrial components on T14V. The fibrillar morphology of this component was revealed by the immunoelectronmicroscopic examination of bacteria incubated with the monoclonal antibodies. The lectin activity associated with these structures was detected when isolated fimbriae were cross-linked with monoclonal antibodies to form immune complexes with agglutination activity for neuraminidase-treated human erythrocytes, a reaction that was inhibited by lactose. Although the 9 monoclonal antibodies differed in their fine specificities, they reacted only with strains of A. viscosus and A. naeslundii that exhibited lactose-inhibitable adherence. These findings indicate that the lectin activity common to these bacteria resides on fimbriae that are antigenically related to those of T14V.