Myeloid-KLF2 knockout neonatal mice experience mortality from lipopolysaccharide in an age-dependent and cell-specific manner

Abstract Background: Preterm neonates exhibit increased mortality from Gram negative sepsis as compared to term neonates. The innate immune system is at a critical phase of development during the neonatal period. Mechanisms underlying activation of the preterm neonatal innate immune response are poorly understood. Our prior data has shown that Kruppel-like factor (KLF)-2 is a critical transcription factor to maintain murine myeloid cells in a quiescent state. We hypothesize that myeloid KLF2 plays a critical role in the neonatal immune response in Gram negative sepsis. Methods: Preterm neonatal (P4) and term neonatal (P12) myeloid KLF2 knockout (MyK2KO) and age matched Cre mice were given 5ug/gm of E. coli O55:B5 lipopolysachharide (LPS) via intraperitoneal (i.p.) injection. For cell depletion studies, antibodies were injected i.p. 24 hours prior to LPS injection, followed by a repeat dose 24h after LPS. Ly6G antibody was used for neutrophil depletion, CD115 for monocyte depletion and equal dose of both for depletion of both cell lines. Results: P4 MyK2KO mice have significantly increased mortality within 48 h of LPS exposure as compared to P4 Cre mice (81% vs 41%, n=19, p<0.01 χ2test). At P12, there is 100% survival of both groups of mice. Depletion of either neutrophils, monocytes or both together, decreased the mortality in P4 MyK2KO mice from 81% to 55%. Conclusion: Preterm neonatal mice lacking myeloid KLF2 have an exaggerated response to LPS as compared to term neonatal MyK2KO or age-matched control mice. In vivo depletion of neutrophils, monocytes or both prior to LPS attenuates this response. Future studies will focus on the mechanism underlying the postnatal age-specific and cell-specific role of KLF2 in the neonatal innate immune response. Supported by grants from Rainbow Faculty Pilot Grant (Mukherjee PI) and NIH (R01 HL142647 Nayak PI)