The cell envelope structure of Gram-negative bacteria is unique, composed of two lipid bilayer membranes and an aqueous periplasmic space sandwiched in between. The outer membrane constitutes an extra barrier to limit the exchange of molecules between the cells and the exterior environment. Donnan potential is a membrane potential across the outer membrane, resulted from the selective permeability of the membrane, which plays a pivotal role in the permeability of many antibiotics. In this review, we discussed factors that affect the intensity of the Donnan potential, including the osmotic strength and pH of the external media, the osmoregulated periplasmic glucans trapped in the periplasmic space, and the displacement of cell surface charges. The focus of our discussion is the impact of Donnan potential on the cellular permeability of selected antibiotics including fluoroquinolones, tetracyclines, β-lactams, and trimethoprim.

Histones are cationic nuclear proteins that are essential for the structure and functions of eukaryotic chromatin. However, extracellular histones trigger inflammatory responses and contribute to death in sepsis by unknown mechanisms. We recently reported that inflammasome activation and pyroptosis trigger coagulation activation through a tissue-factor (TF)-dependent mechanism. We used a combination of various deficient mice to elucidate the molecular mechanism of histone-induced coagulation. We showed that histones trigger coagulation activation in vivo, as evidenced by coagulation parameters and fibrin deposition in tissues. However, histone-induced coagulopathy was neither dependent on intracellular inflammasome pathways involving caspase 1/11 and gasdermin D (GSDMD), nor on cell surface receptor TLR2- and TLR4-mediated host immune response, as the deficiency of these genes in mice did not protect against histone-induced coagulopathy. The incubation of histones with macrophages induced lytic cell death and phosphatidylserine (PS) exposure, which is required for TF activity, a key initiator of coagulation. The neutralization of TF diminished the histone-induced coagulation. Our findings revealed lytic cell death as a novel mechanism of histone-induced coagulation activation and thrombosis.

IRF4 is a transcription factor within the interferon regulatory factor family that controls key aspects of lymphocyte differentiation and adaptive immunity. The heterozygous IRF4 p.Thr95Arg (p.T95R) variant affecting the DNA-binding domain was recently identified to cause a new inborn error of immunity, but the longitudinal clinical course and therapeutic implications remain incompletely defined. We performed detailed clinical characterization and follow-up of all 10 known patients. Each presented with early-onset combined immunodeficiency characterized by hypo- or agammaglobulinemia and marked susceptibility to opportunistic infections. Pulmonary disease was universal, and gastrointestinal involvement was associated with a more severe clinical course. Four patients underwent hematopoietic stem cell transplantation; two survived, and two died. Notably, both deaths occurred in patients transplanted in the setting of active infection. These findings define IRF4 p.T95R as a profound combined immunodeficiency with high infectious burden and demonstrate that disease severity and intervention timing may contribute to transplant outcomes, supporting early diagnosis and timely transplantation before uncontrolled infection.