Immune checkpoint blockade (ICB) has heralded a new era in cancer therapy. Research into the mechanisms underlying response to ICB has predominantly focused on T cells; however, effective immune... Show moreImmune checkpoint blockade (ICB) has heralded a new era in cancer therapy. Research into the mechanisms underlying response to ICB has predominantly focused on T cells; however, effective immune responses require tightly regulated crosstalk between innate and adaptive immune cells. Here, we combine unbiased analysis of blood and tumors from metastatic breast cancer patients treated with ICB with mechanistic studies in mouse models of breast cancer. We observe an increase in systemic and intratumoral eosinophils in patients and mice responding to ICB treatment. Mechanistically, ICB increased IL-5 production by CD4(+) T cells, stimulating elevated eosinophil production from the bone marrow, leading to systemic eosinophil expansion. Additional induction of IL-33 by ICB-cisplatin combination or recombinant IL-33 promotes intratumoral eosinophil infiltration and eosinophil-dependent CD8(+) T cell activation to enhance ICB response. This work demonstrates the critical role of eosinophils in ICB response and provides proof-of-principle for eosinophil engagement to enhance ICB efficacy. Show less
Heesterbeek, D.A.C.; Martin, N.I.; Velthuizen, A.; Duijst, M.; Ruyken, M.; Wubbolts, R.; ... ; Bardoel, B.W. 2019
Gram-negative bacteria are refractory to the action of many antibiotics due to their impermeable outer membrane. An important player of the immune system is the complement system, a protein network... Show moreGram-negative bacteria are refractory to the action of many antibiotics due to their impermeable outer membrane. An important player of the immune system is the complement system, a protein network in serum that directly kills Gram-negative bacteria through pore-formation by the Membrane Attack Complexes (MAC). We here show that the MAC rapidly perforates the outer membrane but that inner membrane damage, which is essential for killing, is relatively slow. Importantly, we demonstrate that MAC-induced outer membrane damage sensitizes Gram-negative bacteria to otherwise ineffective, Gram-positive-specific, antimicrobials. Synergy between serum and nisin was observed for 22 out of 53 tested Gram-negative clinical isolates and for multi-drug resistant (MDR) blood isolates. The in vivo relevance of this process is further highlighted by the fact that blood sensitizes a MDR K. pneumoniae strain to vancomycin. Altogether, these data imply that antibiotics that are considered ineffective to treat infections with Gram-negatives may have different functional outcomes in patients, due to the presence of the complement system. Show less
