Cytokine changes over time in patients who did and did not develop pneumonitis. IL-6, IL-7, IL-8, and interferon-γ serum levels were measured by Luminex immunoassays and are depicted separately for patients with (n = 12) and without pneumonitis (n = 27) onset while on idelalisib and entospletinib and for patients treated with entospletinib monotherapy (n = 15). Data are represented as fold change from baseline ×100. Greater elevations of cytokines/chemokines associated with immune cell activation support immunologic mechanisms for the observed pneumonitis pathogenesis. Cell recruitment and Th1 responses, as well as a greater median increase in cytokines/chemokines associated with pneumonitis, were observed in patients with pneumonitis onset compared with patients without pneumonitis onset. *Patients treated on the open-label phase 2 trial of entospletinib.²¹