Three days post viral infection CD8 T cells (red) re-arrest with antigen presenting cells (cyan), where they are supplied with IL-2 by CD4 T cells (yellow), which migrate in a stop and go pattern.

Cell proliferation may be assessed by flow cytometry. Cell are labelled with the dye CFDA ... The effect of lymphopenia upon antigen-driven proliferation of auto-reactive CD4 T-cells (or CD4 +ve ...