Binding of Bio-GAS (A) to normal blood lymphocyte subsets, (B) to purified tonsil B cells of different size obtained at different Percoll gradients, and (C) to leukocyte cell lines. In (A), two-color immunofluorescence with Bio-GAS/SA-FITC and PE-conjugated CD3, CD56, and CD19 MoAbs was performed; lymphocytes were gated from PBMCs on the basis of forward and side scatter parameters and they contained no detectable CD14⁺ cells. In (B), the forward scatter dot marker was established arbitrarily. These purified tonsil B cells mostly expressed (≥90%) CD19 and (70% to 85%) i antigen as detected by CABER,10,11 13 whereas they contained ≤4% of CD3⁺ cells and no detectable CD56⁺ cells and CD14⁺ cells. In (C), the immunofluorescence technique was as described in Fig 1.