Analysis of CD4⁺ T cells for perforin expression.

Perforin expression was examined by flow cytometric analysis in CD4⁺ and CD8⁺ CTLs. A gate was placed on CD3⁺ events. The gray shades indicate the background staining by the control isotype antibody. Note that the CD8⁺ line PD-F8, but not the CD4⁺ lines ND-R4, PD-F4, and TD-B4, stained positive for perforin. A representative of 2 independent experiments is shown.