Combined TLR/CD40 Stimulation Mediates Potent Cellular Immunity by Regulating Dendritic Cell Expression of CD70 In Vivo

Abstract

We previously showed that immunization with a combination of TLR and CD40 agonists (combined TLR/CD40 agonist immunization) resulted in an expansion of Ag-specific CD8 T cells exponentially greater than the expansion observed to immunization with either agonist alone. We now show that the mechanism behind this expansion of T cells is the regulated expression of CD70 on dendritic cells. In contrast to previous results in vitro, the expression of CD70 on dendritic cells in vivo requires combined TLR/CD40 stimulation and is not significantly induced by stimulation of either pathway alone. Moreover, the exponential expansion of CD8+ T cells following combined TLR/CD40 agonist immunization is CD70 dependent. Thus, the transition from innate stimuli (TLRs) to adaptive immunity is controlled by the regulated expression of CD70.

CD27 Instructs CD4+ T Cells to Provide Help for the Memory CD8+ T Cell Response after Protein Immunization

“…Bullock and Yagita showed that the capacity of CD40-stimulated, peptideloaded DC to elicit a CD4 ϩ T cell-independent primary CD8 ϩ T cell response was fully dependent on the collective functions of CD70 and CD80/CD86 (14). Using blocking Ab in vivo, other authors have corroborated the importance of CD70 on DC for CD8 ϩ T cell priming using protein immunization and infection models (9,15,16). These findings suggest that induction of CD70 expression is an important aspect of DC licensing by CD4 ϩ T cells.…”

“…CD70 can be expressed by activated T and B cells and by all conventional DC subsets upon their maturation (6 -9). CD70 expression on both CD8 ϩ and CD11b ϩ DC is optimal after combined stimulation of TLR and CD40 (9), which reflects pathogen recognition and interaction with cognate CD4 ϩ T cells, via CD40L. In such a scenario, DC are functionally modified ("licensed") to support the CD8 ϩ T cell response (10 -13).…”

IL-27 is required for shaping the magnitude, affinity distribution, and memory of T cells responding to subunit immunization

“…Here, we demonstrate that subunit vaccines are uniquely and unexpectedly dependent on the cytokine IL-27 for making strong T-cell responses. (combined TLR/CD40 vaccination) (23,24). In contrast to other forms of vaccination/immunization, T-cell intrinsic stimulation from classical Signal 3 cytokines such as type I IFN or IL-12 were not required for T-cell expansion, polarization, or memory generation (25,26).…”

“…This failure to recapitulate the magnitude of the T-cell response to Poly I:C/αCD40 indicates that IL-27 cannot completely replicate the complex inflammatory environment instigated by the TLR agonist. We and others previously published on an important role for CD70-CD27 interactions in the T-cell response to combined TLR/ CD40 immunization (24,25,54) as well as to infectious challenge/ vaccination (55)(56)(57)(58). Because IL-27 and CD27 separately are required for maximal T-cell responses after subunit vaccination, neither alone is therefore sufficient for maximal T-cell expansion.…”

Generating a Battery of Monoclonal Antibodies Against Native Green Fluorescent Protein for Immunostaining, FACS, IP, and ChIP Using a Unique Adjuvant

“…(7) Characterization of these eight MAbs is presented here. All eight proved effective for immunostaining fixed cell preparations, six for staining sections of paraffin-embedded tissue, all for fluorescence-activated cell sorting (FACS), five for IP and seven for ChIP.…”