A non-lectin-like mechanism by which Fusobacterium nucleatum 10953 adheres to and activates human lymphocytes

Most (approximately 80%) strains of Fusobacterium nucleatum adhere to human erythrocytes in a lectin-like manner that is strongly inhibited by N-acetyl-D-galactosamine (GalNAc). In this study, we investigated the capacity of F. nucleatum 10953, a strain that is weakly inhibited by GalNAc, to adhere to and activate human lymphocytes in vitro. Experiments using [3H]-labeled bacteria and scanning electron microscopy clearly showed that 10953 adhered to lymphocytes and that adherence was blocked by L-arginine+GalNAc greater than L-arginine much greater than GalNAc. Adherence was Ca(2+)-dependent, inhibited by pretreatment of the bacteria with proteases or heat, and unaffected by paraformaldehyde fixation of the bacteria. Strain 10953 induced lymphocyte mitogenesis that was blocked by L-arginine but not by GalNAc. These results suggest that certain strains of F. nucleatum, such as 10953, express a distinct, non-lectin-like mechanism by which they adhere to and activate lymphocytes. Activation of lymphocytes may be an important mechanism in the pathogenesis of periodontal diseases associated with these bacteria.