“…However, in other studies (Wolberg and DeWitt, 1969) antisomatic 0 antibodies, raised against the 0-antigenic polysaccharide side chains of the lipopolysaccharide were opsonic and protective for a strain containing K antigen. In addition, several investigators have reported that antisera raised in horses and rabbits against rough mutants of Enterobacteriaceae (strains with lipopolysaccharides lacking 0-antigenic side chains) and containing antibodies against the core-glycolipid antigen, could passively transfer broad-spectrum protection against parenteral challenge with smooth strains (with 0-antigenic side chains) of Enterobacteriaceae (McCabe, 1972;Ziegler et al, 1973;Young, Stevens and Ingram, 1975). These antibodies appear to act primarily as anti-endotoxic antibodies rather than as opsonins .…”