Isolation of CD4+ T cells.
CD4+ T cells were isolated from blood of healthy human volunteers using the anti-CD4 magnetic beads (Dynal, Hamburg, Germany) as previously described [60]. The purity of CD4+ T cells was initially tested by FACS and was >/= 95%. Monoclonality of T cell clones was confirmed by TCR-chain mapping and was identified to be Vbeta8 positive. The clones were characterized by high IL-4 secretion. 
