Extrinsic Phagocyte-Dependent STING Signaling Dictates the Immunogenicity of Dying Cells.

The ability of dying cells to activate antigen-presenting cells (APCs) is carefully controlled to avoid unwarranted inflammatory responses. Here, we show that engulfed cells containing cytosolic double-stranded DNA species (viral or synthetic) or cyclic di-nucleotides (CDNs) are able to stimulate APCs via extrinsic STING (stimulator of interferon genes) signaling, to promote antigen cross-presentation. In the absence of STING agonists, dying cells were ineffectual in the stimulation of APCs in trans. Cytosolic STING activators, including CDNs, constitute cellular danger-associated molecular patterns (DAMPs) only generated by viral infection or following DNA damage events that rendered tumor cells highly immunogenic. Our data shed insight into the molecular mechanisms that drive appropriate anti-tumor adaptive immune responses, while averting harmful autoinflammatory disease, and provide a therapeutic strategy for cancer treatment.

Pharmacokinetics and Biodistribution Study of 7A7 Anti-Mouse Epidermal Growth Factor Receptor Monoclonal Antibody and Its F(ab')(2) Fragment in an Immunocompetent Mouse Model.

Immunocompetent mice, Fc receptor γ-chain deficient mice (Fcer1g(-/-)), and molecular tools as F(ab')(2) bivalent fragments appear as the most suitable biological models to study the mechanisms of the action of anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (mAbs). In vivo experiments contrasting antitumor effects of whole Abs and their bivalent fragments commonly involve a previous comparative pharmacokinetics study. In this paper, pharmacokinetics and biodistribution of an anti-mouse EGFR Ab were assessed using immunocompetent mice. (125)I-labeled 7A7 mAb holds an elimination half-life (t(1/2)ß) of 23.1 h in C57BL/6 mice. Accumulation of mAb was found in liver, spleen, kidneys, and mostly in lungs. We used an ELISA method to determine the t(1/2)ß of a 7A7 mAb using the same experimental setting. Results from this new analysis revealed a t(1/2)ß of 23.9 h, supporting this method as a safer and easier system to evaluate pharmacokinetics parameters of mAbs targeting mouse EGFR. Using this system we also studied pharmacokinetics of 7A7 F(ab')(2) fragment. A tenfold difference between the mAb and fragment t(1/2)ß was found. These data support the use of the 7A7 F(ab')(2) fragment in in vivo studies to explore the contribution of the EGFR signaling blockade and the Fc region to the antitumor effect of 7A7 mAb in this autologous scenario.