PI16 and obstructive sleep apnea syndrome: To assess to what extent PI16+ RCs modulate T cell activation and whether PI16+ RC-derived factors affect T cell functionality, tonsillar PI16+ RCs from patients with OSA or tonsillitis were co-cultured with autologous CD3+ T cells in the presence or absence of the surface molecule-cross-linking lectin phytohemagglutinin (PHA).