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. Author manuscript; available in PMC: 2015 May 1.
Published in final edited form as: Wiley Interdiscip Rev Nanomed Nanobiotechnol. 2014 Mar 10;6(3):298–315. doi: 10.1002/wnan.1263

FIGURE 1.

FIGURE 1

Dendritic cells initiate T cell immunity in the lymph nodes. A mature DC encounters antigen in the lymph nodes where it processes and cross-presents the antigen in the context of peptide/MHC molecules to T cells. A T cell bearing a receptor (TCR) of cognate specificity to the presented peptide/MHC is induced by TCR stimulation (signal 1) to express CD40L, leading to activation of the DC through CD40 engagement. DC activation results in increased costimulation to the T cell through the B7/C28 pathway (signal 2). TCR stimulation in the presence of CD28 signaling results in T cell activation, IL-2 dependent proliferation, and differentiation into an effector T cell. The cytokine milieu directs T cell differentiation along one of the helper T cell (TH) lineages.