Combined preparations, and pharmaceutical compositions, comprising: (a) LAG-3 protein, or a derivative thereof that is able to bind to MHC class II molecules; and (b) a programmed cell death protein-1 (PD-1) pathway inhibitor, are described. The PD-1 pathway inhibitor, such as an anti-PD-1 antibody or an anti-PD-L1 antibody, and a soluble derivative of LAG-3, acting as an APC activator, together synergistically activate T cells (in particular, CD8+ T cells). Use of the combined preparations and compositions as medicaments, in particular for the treatment of cancer or infection, and to methods for the treatment of cancer or infection, is described.