Expression of CD21 on the surface of labeled (——) PBLs and (- - -) TDLs harvested from blood and lymph 3 to 18 days after intravenous injection. PBLs and TDLs migrating to efferent prescapular lymph show similar staining patterns. In contrast, CD21 expression is markedly higher on labeled TDLs later recovered from the peripheral blood than on labeled PBLs (representative data from 1 animal).