Neutrophils Are More Effective than Monocytes at Phagosomal Containment and Killing ofListeria monocytogenes

Abstract

Neutrophils and inflammatory monocytes are innate immune cells essential for protection during Listeria monocytogenes infection. Although certain functions have been generally assigned to each of the cells, similarities and differences in functions necessary for bacterial clearance have not previously been investigated. In the current study, phagocytosis, phagosomal containment, bacterial killing, and cytokine production by neutrophils and monocytes during L. monocytogenes infection were studied. Data obtained via in vitro studies show that neutrophils are more effective at L. monocytogenes uptake, phagosomal containment, and killing than monocytes. However, monocytes were found to be more effective at cytokine production during L. monocytogenes infection, in vivo. Additionally, the data demonstrated that neutrophils and monocytes are also capable of producing IL-1α, a cytokine that does not yet have a clearly defined role during infection with L. monocytogenes. Furthermore, we were able to demonstrate a population of monocytes producing both TNF-α and IL-α, concurrently. This study highlights the multifunctional capabilities of neutrophils and monocytes, further adding to our knowledge of these innate immune cells during L. monocytogenes infection.

Enhanced Susceptibility of ADAP-Deficient Mice to Listeria monocytogenes Infection Is Associated With an Altered Phagocyte Phenotype and Function

“…However, recruited ADAP-deficient neutrophils appear to be inefficient in controlling pathogen growth, suggesting that they were not appropriately activated within the ADAP-deficient immune system. Of note, during Lm infection, monocytes are more efficient than neutrophils in the production of TNF-a and IL-1a (19), which is well in line with our data (Figure 3 and Supplementary Figure 3, left and middle panels). Moreover, production of TNF-a might enhance the ability of neutrophils to take up and kill Lm (19).…”

“…Of note, during Lm infection, monocytes are more efficient than neutrophils in the production of TNF-a and IL-1a (19), which is well in line with our data (Figure 3 and Supplementary Figure 3, left and middle panels). Moreover, production of TNF-a might enhance the ability of neutrophils to take up and kill Lm (19). Our data, however, did not reveal any correlation between TNF-a production and antibacterial function of neutrophils.…”

“…Neutrophils play an important role in the immune response to low dose Lm infection in the liver, while in the spleen neutrophils play a vital role for protection against high dose infection ( 17 ). Moreover, neutrophils are more effective at phagocytosis of Lm than inflammatory monocytes ( 19 ). Of note, tumor necrosis factor (TNF) and especially inducible nitric oxide synthase (iNOS) are essential for the clearance of murine Lm infection ( 20 , 21 ).…”

Preconceptual Priming Overrides Susceptibility to Escherichia coli Systemic Infection during Pregnancy

“…In this context, it is important to also highlight pregnancy-induced changes in the frequency and tissue distribution of innate immune cells, including neutrophil and macrophage cells (28,75,76), both of which participate in protective immunity against E. coli and L. monocytogenes infections (38,(77)(78)(79)(80)(81). The cellular shifts that lead to infection susceptibility during pregnancy are likely linked with changes in systemic and local levels of innate inflammatory cytokines.…”

Cellular mechanisms underlying beneficial versus detrimental effects of bacterial antitumor immunotherapy

“…Altogether, these results demonstrated that PMNs are the primary reservoir for Lm in the TME. This result was unanticipated, as we expected PMNs would rapidly kill phagocytosed Lm, preventing their escape into the cytosol and the expression of RFP [49][50][51] .…”