LAG-3 in (auto)immunity and cancer - Emphasising its role in antigen presenting cells.

The growing popularity of immunotherapy shows a promising future for cancer treatment. However, a significant need to develop new therapeutics that could be successfully used in therapy still remains, especially in "immune-cold" tumors that are not responsive to classic anti-PD-1 treatment. Therefore, the discovery of lymphocyte activation gene-3 (LAG-3) as a new immune checkpoint (IC) molecule that physiologically participates in auto-tolerance mechanisms preventing auto-aggression was a significant milestone in immuno-oncology. Two main approaches aim to introduce LAG-3-directed therapies into clinical practice: anti-LAG-3 antibodies that are meant to inhibit LAG-3 function and recombinant soluble LAG-3 form that aim to activate immune response, especially by interacting with the antigen-presenting cells (APCs). So far, studies show that both approaches may be safe and effective anti-cancer treatment options. This review summarises the role of LAG-3 in immune response and emphasises the role of this IC molecule and its soluble form on APCs function, while also noting the primary physiological function of LAG-3 in autoimmunity and providing a dual perspective of the pros and cons of this novel anti-cancer therapy.