TREM2 and infection: To examine the impact of TREM2 deficiency on T-cell immunity against mycobacteria, we collected mediastinal lymph node cells from WT and Trem2−/− mice at day 14 after the intratracheal infection, and stimulated them with the mycobacterial antigen purified protein derivative (PPD) to analyze their production of interferon (IFN)-γ and IL-17A.