Protection against Gram-negative infection by 'super-active' antigen.

'Super-active' antigens modified antigens released from bacteria which had been phagocytosed and killed by human leucocytes, were found to induce protective responses in mice within 24 h of immunization. At the earliest time (24 h) when immunized mice were protected against lethal intrapertoneal (i.p.) challenge by the bacteria from which which the 'super-active' antigens were made (Proteus mirabilis) the leucocytes of peripheral blood from immunized mice showed enhanced phagocytosis and killing of autologous bacteria and there was an increase in the number of lymphocytes producing anti-proteus antibody. Another mouse protective factor inducing transient protection lasting 1-2 days against lethal i.p. challenge by P. mirabilis was found in preparations of lysed heman leucocytes not engaged in phagocytosis. Burned mice, immunized with 'super-active' antigen preparations were protected against lethal invasive proteus infection, inoculated on to the burn surface, 2 h after burning and immunization.