Mouse model for primary and secondary allergen-specific IgE responses. According to the scheme (upper part) groups of BALB/c mice (A–F, n = 5) were sensitized to 4xP on day 0, blood samples were taken as indicated, and a single boost was given on day 165 with different molecules or PBS (groups A–F) as shown below. In the upper part, sensitization, boost, and sacrifice are indicated by an upward-pointing arrow and the bleedings by a downward-pointing arrow.