Family pedigree and analysis of B cell lymphocytosis. (A) Family pedigree of P1–3. Circles represent females, squares represent males, and slashes through symbols represent deceased individuals. Solid gray symbols indicate those affected with polyclonal B cell lymphocytosis. Solid black symbols denote progression to monoclonal B-CLL in P1. (B) Total lymphocytes, spleen size, and absolute counts of B cells and T cells in peripheral blood from patients were measured over time by flow cytometry. The gray zone delineates the median and normal range (between 10th and 90th percentile) in age-matched individuals. (C) Serum Ig titers in patients were measured over time by ELISA; gray zone delineates median and normal range (between 5th and 95th percentile). (D) H&E staining of spleen, lymph node, and appendix tissue sections from P1, taken at 34 mo of age (right). Control specimens (ctrl) are shown for comparison (left), including an age-matched lymph node biopsy showing reactive follicular hyperplasia. (E) Histochemical analysis of tonsil sections from control reactive tonsil, P2, and P3 stained with H&E, anti-IgD, and anti-CD3. Black arrowheads mark expanded mantle zones in D and E. Representative photographs are shown. Bars, 500 µm.