CD3δ and CD3γ expression in lymphoid populations at different levels of maturation. mRNA from Jurkat T cells, fresh CD34⁺Lin⁺ cells expressing at least one lineage cocktail marker, and CD34⁺Lin⁻DR⁻ cells after 14 days of culture under optimal conditions (IL-2, IL-3, IL-7, KL, SCM, FL) was subjected to PCR analysis for CD3δ and CD3γ expression (A). A low-molecular-weight isoform was detected for each transcript in the cultured CD34⁺Lin⁻DR⁻ cells. Densitometric analysis of the various isoforms was then performed from the autoradiograph (B). The low-molecular-weight isoforms were more predominant in the immature cultured CD34⁺Lin⁻DR⁻ cells and nearly absent in the mature T-cell controls.