Expression of CD21 on the surface of B cells recovered from peripheral blood, lymph, retropharyngeal lymph node, and spleen. Dual-color analysis clearly demonstrates the presence of a pool of CD21⁻ B cells in the peripheral blood that is absent from lymph. A small number of CD21⁻ B cells also appears to be in lymph node and spleen (blood and lymph plots from 1 animal; spleen and lymph node plots from 1 animal).