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. 2021 Mar 29;12:636118. doi: 10.3389/fimmu.2021.636118

Figure 1.

Figure 1

Early and late cellular networks involved in Trm cell differentiation and maintenance. After viral respiratory pneumonia, early pulmonary CD8 TRM cell differentiation is driven by re-encounter with antigen presented via interstitial classic monocytes (mnc) and opposed by alveolar macrophages that maintain lung homeostasis. B cell-dependent tissue-resident CD4 helper T cells (TRH) support TRM cell maintenance through IL-21 dependent survival. TRM intrinsic PD-1 signaling prevents pathology in the absence of infectious virus. Created with BioRender.