CD22/cal has B-cell-specific in vivo cytotoxicity. Male B6 mice received 2 (days 0 and 5) intraperitoneal injections with the conjugate at a calicheamicin dose of 160 μg/kg/injection. B-cell depletion was monitored in individual mice by flow cytometry in BM, spleen, LN, and PB samples on days 12, 20, 30, 35, 40, and 50 after the first injection. Three mice per time point were studied and the results (mean percentages ± SD) are listed in Table 2. (A) Flow cytometry dot plot representation of the data listed in Table 2. Numbers are the percentages of CD22⁺ B cells in PB, spleen, BM, and LNs before and 12 days after 2 injections with CD22/cal. Representative data from one mouse are shown. (B) Day 12 samples were also stained for CD19 expression. (C) Flow cytometric analysis demonstrating that the same population of B cells stained positive for CD22 and CD19 expression in PB, spleen, BM, and LN tissue samples in wild-type B6 mice. Representative data from one mouse are shown.