The mode of action of immunological adjuvants. I. A new method to assess the adjuvant effect of substances as represented by mycobacterial adjuvants.

When mice were sensitized with sheep red blood cells (SRBC), the addition of adjuvant-active substances to the sensitizing antigen resulted in a highly significant increase in the mean diameter of plaques developed by spleen cells as measured by Jerne's plaque technique. The increase in plaque diameter was found to be a good measure for the adjuvant effect of such substances as mycobacterial adjuvants, because the phenomenon is specific, reproducible, sensitive and can be tested using a few number of mice.