The percentage of histamine released from the blood of S. mansoni -infected individuals, pre- and post-treatment, after in vitro stimulation with anti-IgE or schistosome Ag. Histamine-releasability (the maximum level of histamine-release, expressed as the % of total cellular histamine content of the blood of each individual), from the washed blood cells of S. mansoni-infected individuals after in vitro stimulation with either SEA, SWA or anti-IgE. Histamine-releasability in vitro for each infected individual at the pre-treatment time point is compared with that 1-day (black square) and 21-days (open square) after treatment after in vitro stimulation with SEA (Fig 2a), SWA (Fig 2b) and anti-IgE (Fig 2c). Any point that plots on the diagonal line is unchanged from the pre-treatment level. The differences between the levels of histamine-releasability between pre-treatment and 1-day post-treatment were statistically significant for all stimuli. The differences between the levels of histamine-releasability between pre-treatment and 21-days post-treatment were statistically significant and nearly significant for SEA-stimulated and anti-IgE-stimulated histamine release, respectively.