Analysis of the Innate Response to Adjuvants: Characterization of the Draining Lymph Node by Fluorescence-Activated...

A clear index for a response to adjuvants is a change in the cellular composition of lymph nodes draining the site of adjuvant injection (Didierlaurent et al., J Immunol 183:6186-6197, 2009; Caproni et al., J Immunol 188:3088-98, 2012; Desbien et al., Eur J Immunol 1-11, 2014). During the steady state, lymph nodes (LNs) are composed of a fixed ratio of innate and adaptive cells awaiting activation signals from tissue draining lymph. Upon exposure to innate stimulants, lymph nodes undergo dramatic changes. The most apparent change to the lymph node is an increase in size. Antigen-independent activation of naïve T cells and B cells, as a consequence of type I interferon signaling, results in upregulation of CD69 (Sun and Zhang, J. Exp. Med 188:2335-2342, 1998), causing increased retention of cells in the lymph node and transient lymphopenia in the blood (Shiow et al., Nature 440:540-544, 2006). In addition tissue-resident dendritic cells, macrophages, as well as circulating inflammatory monocytes will migrate into draining LNs and display maturation markers associated with activation. Such features can provide powerful discrimination of adjuvant potencies.