TNFRSF9 and neoplasm: Although antagonising co-inhibitory receptors on T cells has proven to be a promising approach for enhancing the anti-tumour activity of CD3+ T-cell redirectors, there is also evidence that agonistic antibodies that are capable of activating co-stimulatory receptors on T cells, including members of the tumour necrosis factor receptor (TNFR) superfamily (e.g., 4-1BB, OX40, GITR, CD27) or immunoglobulin superfamily (e.g., CD28, ICOS), can be used to boost immune responses to CD3+ T-cell-engaging therapies.