PRT/heparin complexes show similar selective binding to B cells. Whole blood from a representative healthy donor was incubated with buffer or antigen (PRT with or without heparin) followed by staining for cell-specific markers and ADA, a monoclonal antibody to PRT/heparin complexes. Mean ± SD of 3 independent experiments is shown. (A) Flow cytometric analyses of peripheral blood leukocytes incubated with buffer, PRT, or PRT/heparin. Flow cytometry was performed on whole blood. Leukocyte subpopulations were defined by forward and side scatter characteristics (lymphocytes, neutrophils, and monocytes). Gated subpopulations were identified by cell-surface markers for T lymphocytes (CD3), B lymphocytes (CD19), neutrophils (CD66b), and monocytes (CD14) on the x-axis and for ADA staining on the y-axis for each antigen. The percentage of ADA-positive cells for each cell lineage appears in the upper right corner of each graph. (B) Graph of cell lineage–specific staining of flow data shown in (A). Binding of ADA to cell lineages incubated with antigen is shown. **P < .005 compared with other data in graph.