Gating strategy used for the detection of 3 distinct immunophenotypes of MBL. Representative immunophenotypes are shown for the 3 categories: CLL-like (CD19⁺CD5⁺CD20^dim), atypical (CD19⁺CD5⁺CD20^bright), and CD5ˉ (CD19⁺CD5ˉ) MBL.^16,17  (A) Two parameter histograms of CD20 peridinin chlorophyll protein complex (PerCP) on x-axis and CD19 (allophycocyanin Cy7 or Pacific Blue) on y-axis were based on initial CD45 expression and SSC signal. B cells are gated for subsequent analysis. (B) κ (FITC) λ (PE) analysis on gated B cells. Cases 97 and 118 have bimodal κ populations showing dim clone and bright polyclonal κ cells. Case 3 shows 80.9% λ population. (C) Gated B cells are displayed on a CD20 vs CD5 plot. Case 97 is subgated on CD20^dim and CD5^+,bright B cells. Case 118 is subgated on CD5⁺ B cells. In case 3, all the B cells are CD5ˉ. (D) Subgated B cells from panel C are displayed on a κ vs λ plot. Case 97 shows 98.6% κ⁺ clone on κ-λ analysis on gated CD20^dim/CD5⁺ B cells. Case 118 shows κ-λ analysis on gated CD5⁺ B cells showing 97.8% κ⁺ clone. Case 3 shows a skewed κ-λ analysis on gated CD5ˉ B cells showing 81.9% λ⁺ cells. FITC, fluorescein isothiocyanate; PE, phycoerythrin.