The majority of circulating human γδT lymphocytes are of the Vγ9Vδ2 lineage, and have TCR specificity for non-peptide phosphoantigens. Previous attempts to stimulate and expand these cells have therefore focussed on stimulation using ligands of the Vγ9Vδ2 receptor, whilst relatively little is known about variant blood γδT subsets and their potential role in cancer immunotherapy.
To expand the full repertoire of γδT without bias towards specific T cell receptors, we made use of artificial antigen presenting cells loaded with an anti gamma delta T cell receptor antibody that promoted unbiased expansion of the γδT repertoire. Expanded cells from adult blood donors were sorted into 3 populations expressing respectively Vδ2 TCR chains (Vδ2+), Vδ1 chains (Vδ1+) and TCR of other delta chain subtypes (Vδ1negVδ2neg)
Both freshly isolated and expanded cells showed heterogeneity of differentiation markers, with a less differentiated phenotype in the Vδ1 and Vδ1negVδ2neg populations. Expanded cells were largely of an effector memory phenotype although there were higher numbers of less differentiated cells in the Vδ1+ and Vδ1negVδ2neg populations. Using neuroblastoma tumor cells and the anti-GD2 therapeutic monoclonal antibody ch14.18 as a model system, all three populations showed clinically relevant cytotoxicity. Whilst killing by expanded Vδ2 cells was predominantly antibody dependent and proportionate to upregulated CD16, Vδ1 cells killed by antibody independent mechanisms.
In conclusion we have demonstrated that polyclonal expanded populations of γδT cells are capable of both antibody dependent and independent effector functions in neuroblastoma.