Mice were exposed to A. fumigatus according to the schedule shown in figure 1. At days 0, 3, 5, 7, 9, 11, and 13 the lungs were removed and immediately processed into single cell suspension. Scatter properties were used to identify lymphocytes followed by staining with anti-CD19/anti-CD23 antibodies to identify conventional B2 lymphocytes. (A and B) The total percentage of CD19+CD23+ B2 cells in the lungs of day 0 (sensitized, unchallenged with A. fumigatus) and day 5 BALB/c mice. (C) Total number of CD19+CD23+ B2 cells in the lungs of day 0 and A. fumigatus challenged BALB/c mice. n=4–5 mice/group and all the lung sections were pooled together for antibody staining.