Representative allogeneic MLRs monitoring the depletion of residual APCs for the different steps of the naive CD4+ or CD8+ T cell purification protocol. The proliferation of CD4+ T lymphocytes (responder cells) stimulated for 4 days with irradiated preparations of PBMC, bulk CD4+ T cells (CD4+) or MHC II depleted naive CD4+ T cells (CD4+ RA+) from another healthy donor (stimulator cells) measured in triplicate by an ELISA-based BrdU incorporation assay are shown. As a negative control (neg.), responder cells were incubated without stimulator cells. The mean OD₄₀₅ values for the uptake of BrdU are shown.