UA may induce growth-promoting antibodies. (A) In vivo tumor growth of MMC tumor cells following intratumoral injection (day 0) of sera from naive animals or from animals from either pretreated with irradiated tumor with (T + UA) or without (T) uric acid. Calculated from 3 separate tumors for each data point. Curves overlap. (B) The thymidine incorporation in live MMC tumor cells exposed to media (■) or various concentrations of serum from animals treated with UA alone (U alone, ▴), irradiated tumor alone (T, ♦), or with UA (T + UA, •). Each determination represents the mean (± SEM) of 3 determinations; *P = .01.