Responses of Tg and WT mice to antigenic challenges. (A) Ig levels in sera of WT and Tg mice. Levels of serum Ig subclasses of mice 5 to 9 months of age (both sexes) were measured by ELISA. Data points indicate individual mice. Statistical (P) values assessing the differences in Ig levels between the 2 groups of mice are indicated at the bottom. (B) Levels of TNP-specific Ab among different Ig classes in sera of preimmune (PI) mice and mice immunized with the indicated TI-I or TI-II Ag as measured by ELISA. ○ indicate WT mice; ●, Tg/+ mice. (C) Levels of TNP-specific Ab among different Ig classes in sera of mice after primary (1⁰) and secondary (2⁰) immunizations with the TD Ag, TNP-KLH, as measured by ELISA. ○ indicate WT mice; ●, Tg/+ mice.