Expression of Tcl1 mRNA in flow-sorted lymphocyte subpopulations from bone marrow, thymus, spleen, peripheral blood, and lymph nodes of wild-type mice. For each lymphocyte subpopulation, 5 × 10⁵ cells were used for total RNA isolation. Pro-B cells were defined as B220⁺CD43⁺IgM^-, pre-B cells as B220⁺CD43^-IgM^-, immature B as B220⁺IgM⁺IgD^-, mature B as B220⁺IgM⁺IgD⁺. The double-positive (DP) thymocytes were defined as CD4/8 double-positive. The CD4/8 double-negative (DN) thymocytes were further subdivided based on differential CD25 and CD44 expression: DN-A, CD4^-CD8^-CD44⁺CD25^-; DN-B, CD4^-CD8^-CD44⁺CD25⁺; DN-C, CD4^-CD8^-CD44^-CD25⁺; DN-D, CD4^-CD8^-CD44^-CD25^-. Splenic B cells were divided into 3 subpopulations based on expression of the B220, CD21, and CD23 cell-surface markers: MZ, marginal zone B cells (B220⁺CD21^hiCD23^int), FO, follicular B cells (B220⁺CD21^intCD23^hi); NF, newly formed B cells (B220⁺CD21^loCD23^lo). Peripheral blood mononuclear cells are designated PBMCs.