The immune enhancing effect of local TNF, expressed in the lungs, during pneumonia caused by Klebsiella has been demonstrated in several ways: treatment with various anti-TNF strategies [26, 31] and genetic deletion of the gene encoding TNF or TNF receptor type I [28] resulted in increased bacterial loads during Klebsiella pneumonia, and conversely, intrapulmonary delivery of a TNF agonist peptide augmented host defense after infection with K. pneumoniae via the airways [33]. Here, TNF is linked to susceptibility to pneumonia measurement.