Ryan Swan

MyD88-dependent expansion of an immature GR-1+CD11b+ population induces T cell suppression and Th2 polarization in sepsis

Polymicrobial sepsis alters the adaptive immune response and induces T cell suppression and Th2 immune polarization. We identify a GR-1+CD11b+ population whose numbers dramatically increase and remain elevated in the spleen, lymph nodes, and bone marrow during polymicrobial sepsis. Phenotypically, these cells are heterogeneous, immature, predominantly myeloid progenitors that express interleukin 10 and several other cytokines and chemokines. Splenic GR-1+ cells effectively suppress antigen-specific CD8+ T cell interferon (IFN) γ production but only modestly suppress antigen-specific and nonspecific CD4+ T cell proliferation. GR-1+ cell depletion in vivo prevents both the sepsis-induced augmentation of Th2 cell–dependent and depression of Th1 cell–dependent antibody production. Signaling through MyD88, but not Toll-like receptor 4, TIR domain–containing adaptor-inducing IFN-β, or the IFN-α/β receptor, is required for complete GR-1+CD11b+ expansion. GR-1+CD11b+ cells contribute to sepsis-induced T cell suppression and preferential Th2 polarization.

Apoptosis in Sepsis: Mechanisms, Clinical Impact and Potential Therapeutic Targets

The inability of present therapies to mitigate the devastating effects of sepsis and multiple organ failure in the critically ill patient indicates that more knowledge of the pathophysiology of sepsis is needed if we are to develop better, more effective interventions. This review will examine the concept that a portion of the immune and organ dysfunctions encountered in the septic rodent/ patient is a reflection of not only the types of cells stimulating/ mediating the apoptotic response, but also the varying capacity of the target cell in a given tissue/ organ to perceive these death receptor stimuli as either an apoptotic, inflammatory and/or necrotic signal. We hope the discussion of such studies provides not only new insight into the pathobiology of sepsis, but also suggests possible therapeutic targets for the management of this devastating condition.