The use of IL-2 to expand Vγ9Vδ2 T cells in vivo has the disadvantage of substantial IL-2 toxicity and the potential for expansion of regulatory T cells (Tregs), which may inhibit anti-tumour immunity (although both of these latter advantages are negated if IL-2 is used after adoptive therapy of Vγ9Vδ2 T cells). This evidence concerns the gene IL2 and neoplasm.