Induction of a protective immunity in mice against Escherichia coli by phenothiazines, 10-[n-(phthalimido)alkyl]-2-substituted-10H-phenothiazines and 1-(2-chloroethyl)-3-(2-substituted-10H-phenothiazines-10-yl)alkyl-1 -ureas .

Abilities of five phenothiazines, six 10-[n-(phthalimido)alkyl]-2-substituted-10H-phenothiazines and six 1-(2-chloroethyl)-3-(2-substituted-10H-phenothiazines-10-yl)alkyl-1- ureas to induce anti-Escherichia coli activity in mice were compared. Seventeen compounds tested in this study had no antibacterial effect in direct contact with Escherichia coli using the disk diffusion method except chlorpromazine (4) with low growth inhibitory action. The pretreatment of mice with several phenothiazines, 10-[n-(phthalimido)alkyl]-2-substituted-10H-phenothiazines or 1-(2-chloroethyl)-3-(2-substituted-10H-phenothiazines-10-yl)alkyl-1- ureas protected the animals from lethal infection of Escherichia coli to various extents. On the basis of these experiments, we assume that the protective effect against Escherichia coli infection might be due to the immunopotentiation or macrophage inducing activity by the compounds, or inactivation of lymphokines induced by the bacteria. Since the infection preventing effect of the tested phenothiazines depends on the chemical structures, the specificity of the biological process can be assumed.