Cell surface expression of λ and κ light chains of primary lymphocytes and preparation of BCR^- B cells. (A) Primary lymphocytes were isolated from nasal adenoids and stained for cell surface expression of the immunoglobulin light chains λ and κ. Most cells were either single λ- or κ-positive BCR⁺ B cells, whereas a smaller fraction was double negative for both immunoglobulin light chains. (B) The lymphocyte preparation was depleted by magnetic sorting with λ- and κ-specific antibodies indirectly coupled to magnetic beads, and the BCR^- fraction was again analyzed for cell surface expression of λ and κ light chains. (C) The BCR^- population consisted of a smaller CD21⁺ B-lymphocyte fraction, whereas CD3⁺ T lymphocytes dominated. CD3^-/CD21^- cells are probably monocytes, which were not further analyzed. (D) In a second approach primary lymphocytes from adenoids were analyzed for surface expression of CD19 and CD77, revealing the initial fraction of GC B cells. (E) The lymphocyte preparation was depleted with CD3, λ- and κ-specific antibodies, enriched for CD77 surface-positive GC B cells, and again analyzed for light chain cell surface expression. (F) Prior to EBV infection, the cells were characterized for their expression of CD77 and CD19, indicating the germinal center origin of the surface BCR^- B-cell preparation. Quadrant statistics based on intact cells in the lymphocyte gate by forward and sideward scatter criteria are depicted in the top right-hand corner of each FACS plot.