As tumour-reactive cells typically only comprise a small fraction of all TIL, TIL therapy is mediated by culture of pooled TIL with autologous tumour cells, with those TIL sub-pools that exhibit anti-tumour responsiveness (for instance via the production of IFN-g) allowed to briefly expand in situ (to enrich for antigen-specificity) then polyclonally re-expanded (for instance through stimulation using OKT3 and interleukin-2) [27,135]. The gene discussed is IL2; the disease is neoplasm.