[Bacterial surface and phagocytosis].

Phagocytosis is a host's front line of cellular defence against bacteria. Some anatomical structures of the bacterial envelope may hinder this cellular activity. Amongst the most important constituents of the cell envelope, the capsule plays a very important role, its biochemical components being polysaccharide (pneumococcus, meningococcus), M proteins (streptococcus, yersinia, E. coli), mucopeptide (staphylococcus) or hyaluronic acid (streptococcus, Treponema pallidum). Complement plays an outstanding role by increasing the phagocytosis index. The studies of the different factors of the complement show that the degree of phagocytosis is correlated with the amount of C3 fixed on the surface of the bacteria. We still do not know the exact nature of the cell receptors, but the surface properties of the host cell and of the bacteria determine the contact angle which is of importance in this process.