Highlights of the advances in basic immunology in 2011

In this review, we summarize the major fundamental advances in immunological research reported in 2011. The highlights focus on the improved understanding of key questions in basic immunology, including the initiation and activation of innate responses as well as mechanisms for the development and function of various T-cell subsets. The research includes the identification of novel cytosolic RNA and DNA sensors as well as the identification of the novel regulators of the Toll-like receptor （TLR） and retinoic acid-inducible gene I （RIG-I）-Iike receptor （RLR） signaling pathway. Moreover, remarkable advances have been made in the developmental and functional properties of innate lymphoid cells （I LCs）. Helper T cells and regulatory T （Treg） cells play indispensable roles in orchestrating adaptive immunity. There have been exciting discoveries regarding the regulatory mechanisms of the development of distinct T-cell subsets, particularly Th17 cells and Treg cells. The emerging roles of microRNAs （miRNAs） in T cell immunity are discussed, as is the recent identification of a novel T-cell subset referred to as follicular regulatory T （TFR） cells.

Conditional Knockout of Src Homology 2 Domain-containing Protein Tyrosine Phosphatase-2 in Myeloid Cells Attenuates Renal Fibrosis after Unilateral Ureter Obstruction

Background：Src homology 2 domain-containing protein tyrosine phosphatase-2 （SHP-2） is a kind of intracellular protein tyrosine phosphatase.Studies have revealed its roles in various disease,however,whether SHP-2 involves in renal fibrosis remains unclear.The aim of this study was to explore the roles of myeloid cells SHP-2 in renal interstitial fibrosis.Methods：Myeloid cells SHP-2 gene was conditionally knocked-out （CKO） in mice using loxP-Cre system,and renal interstitial fibrosis was induced by unilateral ureter obstruction （UUO）.The total collagen deposition in the renal interstitium was assessed using picrosirius red stain.F4/80 immunostaing was used to evaluate macrophage infiltration in renal tubular interstitium.Quantitative real-time polymerase chain reaction and enzyme linked immunosorbent assay were used to analyze the production of cytokines in the kidney.Transferase-mediated dUTP nick-end labeling stain was used to assess the apoptotic renal tubular epithelial cells.Results：Src homology 2 domain-containing protein tyrosine phosphatase-2 gene CKO in myeloid cells significantly reduced collagen deposition in the renal interstitium after UUO.Macrophage infiltration was evidently decreased in renal tubular interstitium of SHP-2 CKO mice.Meanwhile,the production of pro-inflammatory cytokines was significantly suppressed in SHP-2 CKO mice.However,no significant difference was observed in the number of apoptotic renal tubular epithelial cells between wild-type and SHP-2 CKO mice.Conclusions：Our observations suggested that SHP-2 in myeloid cells plays a pivotal role in the pathogenesis of renal fibrosis,and that silencing of SHP-2 gene in myeloid cells may protect renal from inflammatory damage and prevent renal fibrosis after renal injury.

Efficient induction of a Her2-specific anti-tumor response by dendritic cells pulsed with a Hsp70L1–Her2_(341–456) fusion protein

Heat shock proteins(HSPs)have been shown to interact with antigen-presenting cells(APCs),especially dendritic cells(DCs).HSPs act as potent adjuvants,inducing a Th1 response,as well as antigen-specific CD8^(+) cytotoxic T lymphocytes(CTL)via cross-presentation.Our previous work has demonstrated that Hsp70-like protein 1(Hsp70L1),a new member of the Hsp70 subfamily,can act as a powerful Th1 adjuvant in a DC-based vaccine.Here we report the efficient induction of tumor antigen-specific T cell immune response by DCs pulsed with recombinant fusion protein of Hsp70L1 and Her2_(341–456),the latter of which is a fragment of Her2/neu(Her2)containing E75(a HLA-A2 restricted CTL epitope).The fusion protein Hsp70L1–Her2_(341–456) promotes the maturation of DCs and activates them to produce cytokines,such as IL-12 and TNF-a,and chemokines,such as MIP-1a,MIP-1b and RANTES.Taken together,these results indicate that the adjuvant activity of Hsp70L1 is maintained in the fusion protein.Her2-specific HLA-A2.1-restricted CD8^(+) CTLs can be generated efficiently either from the Peripheral blood lymphocytes(PBL)of healthy donors or from the splenocytes of immunized HLA-A2.1/K^(b) transgenic mice by in vitro stimulation or immunization with DCs pulsed with the Hsp70L1–Her2_(341–456) fusion protein.This results in more potent target cell killing in an antigen-specific and HLA-A2.1-restricted manner.Adoptive transfer of splenocytes from transgenic mice immunized with Hsp70L1–Her2_(341–456)-pulsed DCs can markedly inhibit tumor growth and prolong the survival of nude mice with Her2^(+)/HLA-A2.1^(+) human carcinomas.These results suggest that Hsp70L1–Her2_(341–456)-pulsed DCs could be a new therapeutic vaccine for patients with Her2^(+) cancer.

CD24 aggravates acute liver injury in autoimmune hepatitis by promoting IFN-γ production by CD4^(+) T cells

The T-cell-mediated immune response is implicated in many clinical hepatic injuries, such as autoimmune hepatitis and acute virus hepatitis. CD24 is widely expressed by different immune cells and plays an important role in the pathogenesis of many autoimmune diseases. However, the role of CD24 in T-cell-mediated liver injury has not been elucidated until now. Here we showed that CD24 deficiency protects mice from concanavalin A (ConA)-induced fulminant liver injury by reducing serum interferon-γ (IFN-γ) levels. CD24 expression by hepatic T cells was markedly increased following ConA challenge. Moreover, decreased IFN-γ production by hepatic CD4^(+) T cells in CD24-deficient mice was detected, which was correlated with downregulated phosphorylation of STAT1 in hepatic tissue. In vitro experiments also supported the conclusion that CD24 deficiency impaired IFN-γ production by CD4^(+) T cells following ConA, CD3/CD28 and phorbol myristate acetate/ionomycin stimulation. Our study suggests that CD24 deficiency confers hepatoprotection by decreasing CD4^(+) T-cell-dependent IFN-γ production in vivo, which suggests that CD24 might be a potential target molecule for reducing clinical hepatitis.

A modified HLA-A^(*)0201-restricted CTL epitope from human oncoprotein (hPEBP4) induces more efficient antitumor responses

We previously identified human phosphatidylethanolamine-binding protein 4(hPEBP4)as an antiapoptotic protein with increased expression levels in breast,ovarian and prostate cancer cells,but low expression levels in normal tissues,which makes hPEBP4 an attractive target for immunotherapy.Here,we developed hPEBP4-derived immunogenic peptides for inducing antigen-specific cytotoxic T lymphocytes(CTLs)targeting breast cancer.A panel of hPEBP4-derived peptides predicted by peptide-MHC-binding algorithms was evaluated to characterize their HLAA2.1 affinity and immunogenicity.We identified a novel immunogenic peptide,P40–48(TLFCQGLEV),that was capable of eliciting specific CTL responses in HLA-A2.1/K^(b) transgenic mice,as well as in peripheral blood lymphocytes from breast cancer patients.Furthermore,amino-acid substitutions in the P40–48 sequence improved its immunogenicity against hPEBP4,a self-antigen,thus circumventing tolerance.We designed peptide analogs by preferred auxiliary HLA-A^(*)0201 anchor residue replacement,which induced CTLs that were crossreactive to the native peptide.Several analogs were able to stably bind to HLA-A^(*)0201 and elicit specific CTL responses better than the native sequence.Importantly,adoptive transfer of CTLs induced by vaccination with two analogs more effectively inhibited tumor growth than the native peptide.These data indicate that peptide analogs with high immunogenicity represent promising candidates for peptide-mediated therapeutic cancer vaccines.