DifferentialRequirements for Soluble and Transmembrane Tumor Necrosis Factor in theImmunological Control of Primary and SecondaryListeria monocytogenesInfection

Abstract

The relative contributions of transmembrane tumor necrosis factor (memTNF) and soluble tumor necrosis factor (solTNF) in innate and adaptive immunity are poorly defined. We examined the capacities of wild-type (WT) mice, TNF^−/−mice, and memTNF mice, which express only transmembrane TNF, to control primary and secondaryListeria monocytogenesinfections. Soluble TNF was not required for induction or maintenance of protective immunity against a low-dose (200-CFU)Listeriainfection. In contrast to TNF^−/−mice, both WT and memTNF mice cleared the bacilli within 10 days and were fully protected against rechallenge with a lethal infective dose. Furthermore, T cells transferred from immune mice, but not from naïve, WT, and memTNF mice, protected TNF^−/−recipients against an otherwise lethal infection. By contrast, infection with a higher dose ofListeria(2,000 CFU) clearly demonstrated that solTNF is required to coordinate an optimal protective inflammatory response. memTNF mice were more susceptible to a high-dose infection, and they exhibited delayed bacterial clearance, increased inflammation, and necrosis in the liver that resulted in 55% mortality. The dysregulated inflammation was accompanied by prolonged elevated expression of mRNAs for several chemokines as well as the macrophage effector molecules inducible nitric oxide synthase and LRG-47 in the livers of memTNF mice but not in the livers of WT mice. These data demonstrated that memTNF is sufficient for establishing protective immunity against a primary low-doseListeriainfection but that solTNF is required for optimal control of cellular inflammation and resistance to a primary high-dose infection. By contrast, memTNF alone is sufficient for resolution of a secondary, high-dose infection and for the transfer of protective immunity with memory T cells.