The adjuvant action of endotoxin on antibody formation to a single injection of a soluble protein antigen (BGG) was demonstrated in an inbred strain of Balb mice. The adjuvant action of endotoxin was expressed in this system by decreasing the induction period and increasing peak titer. The length of time in relation to antigen administration during which endotoxin would exert its adjuvant action was found to be longer in the mouse (from 7 days before to 6 days after antigen) than in previous studies in the rabbit.
The DNA analogue 5-fluoro-2′-deoxyuridine (FUDR) was found to inhibit antibody formation to BGG in these Balb mice when given daily in small doses or in a single large dose 24 or 48 hr after antigen. This single large dose of FUDR was found to be stimulatory to antibody formation when given near the time of antigen injection (1 hr before, with, or 1 hr after) or when given 4 days after antigen injection. No drug-induced tolerance to BGG in adult mice was achieved.