Bacterial sepsis characterised by an immunosuppressive and cytokine storm state is a challenge to treat clinically. While conventional antibiotics have been associated with exacerbating the cytokine storm, the role that bacteriophages may play in immune modulation of sepsis remains unclear. Bacteriophages are bacterial viruses that have the capacity to lyse specific bacteria and hence provide a natural alternative to antibiotics. K. pneumoniae is known to cause sepsis in humans, and in this study we isolated two lytic bacteriophages against this pathogen, one of which was a novel jumbo bacteriophage. We employed THP-1 monocyte cell lines, with different functional phenotypes for the interleukin-1 receptor associated kinase 3 (IRAK3- a cytoplasmic homeostatic mediator and prognostic marker of inflammation), to evaluate the role of the K. pneumoniae bacteriophages in modulating the immune response in-vitro. We showed for the first time that bacteriophages did not stimulate excessive production of tumour necrosis factor alpha, or interleukin-6, in THP-1 monocyte cell lines which displayed varying levels of IRAK3 expression.