Pneumonia is the leading killer of children globally and a significant cause of morbidity and
mortality in the US. Pneumonias due to drug-resistant Enterobacteriaceae are an emerging
problem. Our lab has shown that lung tissue resident memory (TRM) cells, consisting of Th17
and Th1 cells, provide profound protection against hyper-virulent K. pneumoniae strains.
Interestingly, these cells must signal through lung fibroblasts to provide protection as deletion of
IL-17RC in Dermo1+ or Col1a2+ cells compromises TRM efficacy. Based on our prior work and
preliminary results, we hypothesize that vaccine-induced Th17 cells signal lung fibroblasts to
secrete the chemokines responsible for recruiting macrophages to the interstitial compartment
of the lung and improve the ability of local macrophages to clear K. pneumoniae. To test this,
we propose the following aims: Aim 1: Evaluate the response of lung fibroblasts to Th17-
associated cytokines (IL17A, IL17F, TNF) and examine the chemotactic and phenotypic impact
fibroblast-derived signals have on several myeloid/monocyte populations. Aim 2: Evaluate the
dependence of bacterial clearance on vaccine-elicited host TRM populations, fibroblast
signaling, and myeloid cell recruitment and modification in vivo. We propose the macrophage
population recruited via fibroblast signaling is (a) the direct downstream result of establishing
TRM cells, (b) key to vaccine efficacy, and (c) phenotypically and locationally well-suited to
clearance of the pathogen.