Fig. 4. Vectorial transport of HA in T lymphocytes. Polarised T lymphoblasts infected with the influenza virus were fixed and subjected to double-label immunofluorescence analysis with antibodies specific to HA and to ICAM-3, a uropod protein marker, in the absence of a permeabilization step. The bright field image is depicted to show the cell morphology. The uropod and the direction of migration are indicated by an arrowhead and an arrow, respectively. Controls to assess the specificity of the labelling included incubations with control primary antibodies or omission of the primary antibodies. Bar, 5 µm.