Lectin-bearing protoplasts of pseudomonas aeruginosa induce capping in human peripheral blood lymphocytes

The redistribution of surface membrane receptors and cap formation by P. aeruginosa lectins (Ps-GAL, which binds D-galactose, and Ps-MAN, which binds D-mannose and L-fucose) was studied in human peripheral blood lymphocytes by scanning electron microscopy. When Ps-GAL and Ps-MAN-bearing protoplasts of P. aeruginosa were incubated with lymphocytes, cap formation was revealed by the accumulation of protoplasts at one pole of the lymphocyte. No adherence or capping was observed when intact P. aeruginosa cells were used. Pretreatment of the lymphocytes by papain or neuraminidase did not enhance the capping. No capping or adherence of protoplasts to lymphocytes was observed in the presence of D-galactose, while addition of D-mannose had no effect. The inhibitory effect of D-galactose on the adherence and capping in human peripheral lymphocytes by P. aeruginosa protoplasts suggests that the Ps-GAL lectin is responsible for both phenomena.