Juvenile idiopathic arthritis (JIA) is one of the most common inflammatory joint diseases in children. Previous studies have shown that in the oligoarticular subtype of this disease, T cells play a central role in pathogenesis. T cell inhibitory receptors (IRs) seem to play an important role in the development of tolerance and recognition of self and non-self antigens. Ligands binding to these IRs inhibit T cell function and modulate the course of the immune response. In this episode, we meet this month's highlighted Early Career Investigator Erdal Sag, a paediatric rheumatologist at Ankara Training and Research Hospital in Turkey. He and his team designed an ex vivo disease model to examine the effects of different co-inhibitory receptors on the pathogenesis of oligoarticular JIA.