Co-culture of primary human T cells with leukemia cells to measure regulatory T cell expansion

The expansion of regulatory T cells (Tregs) is known to be mediated by cytokines including IL-10 and TGFβ but has additionally been shown to depend on the interaction of the immune receptors ICOSLG and ICOS. Here, we describe a co-culture system which enables quantification of the ability of leukemia cells to induce Treg expansion through secreted cytokines and direct receptor interactions. The protocol is applicable for MHC-matched and -unmatched experiments and allows assessment of Treg expansion without using a mouse model. For complete details on the use and execution of this protocol, please refer to Külp et al. (2022).