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1.  ETO family protein Mtg16 regulates the balance of dendritic cell subsets by repressing Id2 
The Journal of Experimental Medicine  2014;211(8):1623-1635.
Transcriptional cofactor of the ETO family Mtg16 promotes pDCs and restricts cDC differentiation in part by repressing Id2.
Dendritic cells (DCs) comprise two major subsets, the interferon (IFN)-producing plasmacytoid DCs (pDCs) and antigen-presenting classical DCs (cDCs). The development of pDCs is promoted by E protein transcription factor E2-2, whereas E protein antagonist Id2 is specifically absent from pDCs. Conversely, Id2 is prominently expressed in cDCs and promotes CD8+ cDC development. The mechanisms that control the balance between E and Id proteins during DC subset specification remain unknown. We found that the loss of Mtg16, a transcriptional cofactor of the ETO protein family, profoundly impaired pDC development and pDC-dependent IFN response. The residual Mtg16-deficient pDCs showed aberrant phenotype, including the expression of myeloid marker CD11b. Conversely, the development of cDC progenitors (pre-DCs) and of CD8+ cDCs was enhanced. Genome-wide expression and DNA-binding analysis identified Id2 as a direct target of Mtg16. Mtg16-deficient cDC progenitors and pDCs showed aberrant induction of Id2, and the deletion of Id2 facilitated the impaired development of Mtg16-deficient pDCs. Thus, Mtg16 promotes pDC differentiation and restricts cDC development in part by repressing Id2, revealing a cell-intrinsic mechanism that controls subset balance during DC development.
PMCID: PMC4113936  PMID: 24980046
2.  Flt3L-dependence helps define an uncharacterized subset of murine cutaneous dendritic cells 
Skin-derived dendritic cells (DC) are potent antigen presenting cells with critical roles in both adaptive immunity and tolerance to self. Skin DC carry antigens and constitutively migrate to the skin draining lymph nodes (LN). In mice, Langerin-CD11b− dermal DC are a low-frequency, heterogeneous, migratory DC subset that traffic to LN (Langerin-CD11b-migDC). Here, we build on the observation that Langerin-CD11b− migDC are Fms-like tyrosine kinase 3 ligand (Flt3L) dependent and strongly Flt3L responsive, which may relate them to classical DCs. Examination of DC capture of FITC from painted skin, DC isolation from skin explant culture, and from the skin of CCR7 knockout mice which accumulate migDC, demonstrate these cells are cutaneous residents. Langerin-CD11b-Flt3L responsive DC are largely CD24(+) and CX3CR1low and can be depleted from Zbtb46-DTR mice, suggesting classical DC lineage. Langerin-CD11bmigDC present antigen with equal efficiency to other DC subsets ex vivo including classical CD8α cDC and Langerin+CD103+ dermal DC. Finally, transcriptome analysis suggests a close relationship to other skin DC, and a lineage relationship to other classical DC. This work demonstrates that Langerin- CD11b− dermal DC, a previously overlooked cell subset, may be an important player in the cutaneous immune environment.
PMCID: PMC3994898  PMID: 24288007
3.  Correction: Targeting Leishmania major Antigens to Dendritic Cells In Vivo Induces Protective Immunity 
PLoS ONE  2013;8(9):10.1371/annotation/5149bf8e-3843-4865-a726-0ca2820ee8f8.
PMCID: PMC3782404
4.  Targeting Leishmania major Antigens to Dendritic Cells In Vivo Induces Protective Immunity 
PLoS ONE  2013;8(6):e67453.
Efficient vaccination against the parasite Leishmania major, the causative agent of human cutaneous leishmaniasis, requires development of type 1 T-helper (Th1) CD4+ T cell immunity. Because of their unique capacity to initiate and modulate immune responses, dendritic cells (DCs) are attractive targets for development of novel vaccines. In this study, for the first time, we investigated the capacity of a DC-targeted vaccine to induce protective responses against L. major. To this end, we genetically engineered the N-terminal portion of the stress-inducible 1 protein of L. major (LmSTI1a) into anti-DEC205/CD205 (DEC) monoclonal antibody (mAb) and thereby delivered the conjugated protein to DEC+ DCs in situ in the intact animal. Delivery of LmSTI1a to adjuvant-matured DCs increased the frequency of antigen-specific CD4+ T cells producing IFN-γ+, IL-2+, and TNF-α+ in two different strains of mice (C57BL/6 and Balb/c), while such responses were not observed with the same doses of a control Ig-LmSTI1a mAb without receptor affinity or with non-targeted LmSTI1a protein. Using a peptide library for LmSTI1a, we identified at least two distinct CD4+ T cell mimetopes in each MHC class II haplotype, consistent with the induction of broad immunity. When we compared T cell immune responses generated after targeting DCs with LmSTI1a or other L. major antigens, including LACK (Leishmania receptor for activated C kinase) and LeIF (Leishmania eukaryotic ribosomal elongation and initiation factor 4a), we found that LmSTI1a was superior for generation of IFN-γ-producing CD4+ T cells, which correlated with higher protection of susceptible Balb/c mice to a challenge with L. major. For the first time, this study demonstrates the potential of a DC-targeted vaccine as a novel approach for cutaneous leishmaniasis, an increasing public health concern that has no currently available effective treatment.
PMCID: PMC3694010  PMID: 23840706
5.  Treml4, an Ig superfamily member, mediates presentation of several antigens to T cells in vivo, including protective immunity to HER2 protein 
Members of the Trem receptor family (Triggering receptor expressed on myeloid cells) fine-tune inflammatory responses. We previously identified one of these receptors, called Trem-like 4 (Treml4), expressed mainly in the spleen, and at high levels by CD8α+ DCs and macrophages. Like other Trem family members, Treml4 has an immunoglobulin-like extracellular domain and a short cytoplasmic tail that associates with the adaptor DAP12. To follow our initial results that Treml4-Fc fusion proteins bind necrotic cells, we now generated a knock out mouse to assess the role of Treml4 in the uptake and presentation of dying cells in vivo. Loss of Treml4 expression did not impair uptake of dying cells by CD8α+ DCs or cross-presentation of cell-associated antigen to CD8+ T cells, suggesting overlapping function between Treml4 and other receptors in vivo. To further investigate Treml4 function, we took advantage of a newly generated mAb against Treml4, and engineered its heavy chain to express 3 different antigens, i.e., ovalbumin, HIV GAGp24 and the extracellular domain of the breast cancer protein HER2. Ovalbumin directed to Treml4 was efficiently presented to CD8+ and CD4+ T cells in vivo. Anti-Treml4-GAGp24 mAbs, given along with a maturation stimulus, induced Th1 antigen-specific responses which were not observed in Treml4 knock out mice. Also, HER2 targeting using anti-Treml4 mAbs elicited combined CD4+ and CD8+ T cell immunity, and both T cells participated in resistance to a transplantable tumor. Therefore, Treml4 participates in antigen presentation in vivo, and targeting antigens with anti-Treml4 antibodies enhances immunization of otherwise naïve mice.
PMCID: PMC3262937  PMID: 22210914
Dendritic cells; Monocytes/Macrophages; Antibodies; Antigen presentation
6.  Microbial stimulation fully differentiates monocytes to DC-SIGN/CD209+ dendritic cells for immune T cell areas 
Cell  2010;143(3):416-429.
Dendritic cells (DCs), critical antigen presenting cells for immune control, normally derive from bone marrow precursors distinct from monocytes. It is not yet established if the large reservoir of monocytes can develop into cells with critical features of DCs in vivo. We now show that fully differentiated Mo-DCs develop in mice and DC-SIGN/CD209a marks the cells. Mo-DCs are recruited from blood monocytes into lymph nodes by lipopolysaccharide and live or dead gram negative bacteria. Mobilization requires TLR4 and its CD14 coreceptor and Trif. When tested for antigen presenting function, Mo-DCs are as active as classical DCs, including cross presentation of proteins and live gram negative bacteria on MHC I in vivo. Fully differentiated Mo-DCs acquire DC morphology and localize to T cell areas via L-selectin and CCR7. Thus the blood monocyte reservoir becomes the dominant presenting cell in response to select microbes, yielding DC-SIGN+ cells with critical functions of DCs.
PMCID: PMC3150728  PMID: 21029863
7.  New monoclonal anti-mouse DC-SIGN antibodies reactive with acetone-fixed cells 
Journal of immunological methods  2010;360(1-2):66-75.
Mouse DC-SIGN CD209a is a type II transmembrane protein, one of a family of C-type lectin genes syntenic and homologous to human DC-SIGN. Current anti-mouse DC-SIGN monoclonal antibodies (MAbs) are unable to react with DC-SIGN in acetone fixed cells, limiting the chance to visualize DC-SIGN in tissue sections. We first produced rabbit polyclonal PAb-DSCYT14 against a 14-aa peptide in the cytosolic domain of mouse DC-SIGN, and it specifically detected DC-SIGN and not the related lectins, SIGN-R1 and SIGN-R3 expressed in transfected CHO cells. MAbs were generated by immunizing rats and DC-SIGN knockout mice with the extracellular region of mouse DC-SIGN.. Five rat IgG2a or IgM MAbs, named BMD10, 11, 24, 25, and 30, were selected and each MAb specifically detected DC-SIGN by FACS and Western blots, although BMD25 was cross-reactive to SIGN-R1. Two mouse IgG2c MAbs MMD2 and MMD3 interestingly bound mouse DC-SIGN but at 10 fold higher levels than the rat MAbs. When the binding epitopes of the new BMD and two other commercial rat anti-DC-SIGN MAbs, 5H10 and LWC06, were examined by competition assays, the epitopes of BMD11, 24, and LWC06 were identical or closely overlapping while BMD10, 30, and 5H10 were shown to bind different epitopes. MMD2 and MMD3 epitopes were on a 3rd noncompeting region of mouse DC-SIGN. DC-SIGN expressed on the cell surface was sensitive to collagenase treatment, as monitored by polyclonal and MAb. These new reagents should be helpful to probe the biology of DC-SIGN in vivo.
PMCID: PMC2924951  PMID: 20558171
Monoclonal Antibody; Polyclonal Antibody; DC-SIGN; CD209a; Dendritic Cells
8.  Dendritic cells require a systemic type I interferon response to mature and induce CD4+ Th1 immunity with poly IC as adjuvant 
The Journal of Experimental Medicine  2009;206(7):1589-1602.
Relative to several other toll-like receptor (TLR) agonists, we found polyinosinic:polycytidylic acid (poly IC) to be the most effective adjuvant for Th1 CD4+ T cell responses to a dendritic cell (DC)–targeted HIV gag protein vaccine in mice. To identify mechanisms for adjuvant action in the intact animal and the polyclonal T cell repertoire, we found poly IC to be the most effective inducer of type I interferon (IFN), which was produced by DEC-205+ DCs, monocytes, and stromal cells. Antibody blocking or deletion of type I IFN receptor showed that IFN was essential for DC maturation and development of CD4+ immunity. The IFN-AR receptor was directly required for DCs to respond to poly IC. STAT 1 was also essential, in keeping with the type I IFN requirement, but not type II IFN or IL-12 p40. Induction of type I IFN was mda5 dependent, but DCs additionally used TLR3. In bone marrow chimeras, radioresistant and, likely, nonhematopoietic cells were the main source of IFN, but mda5 was required in both marrow–derived and radioresistant host cells for adaptive responses. Therefore, the adjuvant action of poly IC requires a widespread innate type I IFN response that directly links antigen presentation by DCs to adaptive immunity.
PMCID: PMC2715098  PMID: 19564349

Results 1-8 (8)