GM-CSF and IL-4 synergistically trigger dendritic cells to acquire retinoic acid-producing capacity

Abstract

Retinoic acid (RA) produced by intestinal dendritic cells (DCs) imprints gut-homing specificity on lymphocytes and enhances Foxp3+ regulatory T-cell differentiation. The expression of aldehyde dehydrogenase (ALDH) 1A in these DCs is essential for the RA production. However, it remains unclear how the steady-state ALDH1A expression is induced under specific pathogen-free (SPF) conditions. Here, we found that bone marrow-derived dendritic cells (BM-DCs) generated with granulocyte-macrophage colony-stimulating factor (GM-CSF) expressed Aldh1a2, an isoform of Aldh1a, but that fms-related tyrosine kinase 3 ligand-generated BM-DCs did not. DCs from mesenteric lymph nodes (MLN) and Peyer's patches (PP) of normal SPF mice expressed ALDH1A2, but not the other known RA-producing enzymes. Employing a flow cytometric method, we detected ALDH activities in 10–30% of PP-DCs and MLN-DCs. They were CD11chighCD4−/lowCD8αintermediateCD11b−/low F4/80low/intermediateCD45RBlowCD86highMHC class IIhighB220−CD103+. Equivalent levels of aldehyde dehydrogenase activity (ALDHact) and ALDH1A2 expression were induced synergistically by GM-CSF and IL-4 in splenic DCs in vitro. In BM-DCs, however, additional signals via Toll-like receptors or RA receptors were required for inducing the equivalent levels. The generated ALDH1A2+ DCs triggered T cells to express gut-homing receptors or Foxp3. GM-CSF receptor-deficient or vitamin A-deficient mice exhibited marked reductions in the ALDHact in intestinal DCs and the T cell number in the intestinal lamina propria, whereas IL-4 receptor-mediated signals were dispensable. GM-CSF+CD11c−F4/80+ cells existed constitutively in the intestinal tissues. The results suggest that GM-CSF and RA itself are pivotal among multiple microenvironment factors that enable intestinal DCs to produce RA.

Retinoic acid-producing,ex-vivo-generated human tolerogenic dendritic cells induce the proliferation of immunosuppressive B lymphocytes

“…DC generated from PBMC progenitors in the presence of GM-CSF/IL-4 are known to be tolerogenic [51,52] and produce RA [53]. Mechanistically, evidence suggests that RA alone, as well as DC producing RA, maintain [54,55].…”

Human CD1c+ Myeloid Dendritic Cells Acquire a High Level of Retinoic Acid–Producing Capacity in Response to Vitamin D3

“…+ mDCs, but not CD141 high mDCs, express a high level of RALDH2 in response to GM-CSF and VD 3 In search of human DCs that express a high level of RALDH enzymes, different subsets of blood DCs were treated with various factors that have been reported to modulate immunostimulatory activity of DCs (Table I), and ALDH activity was measured with Aldefluor (2,4,5,7,8,12,19). To keep mDCs alive, we added GM-CSF (22) to CD1c + mDCs.…”

“…It has been shown that CD103 + DCs in lamina propria and mesenteric lymph nodes (MLNs) produce RA and thus to promote the generation of gut-homing regulatory T (Treg) cells (3). GM-CSF (4) and RA (4)(5)(6)(7)(8) are pivotal factors to induce mouse DCs to express retinal dehydrogenase (RALDH)2, which is encoded by the aldehyde dehydrogenase 1 family, member A2 (ALDH1A2) gene and converts retinal to RA. IL-4 (4, 9) and TLR ligands (2,4,5,(10)(11)(12) augment the expression of RALDH2.…”

“…GM-CSF (4) and RA (4)(5)(6)(7)(8) are pivotal factors to induce mouse DCs to express retinal dehydrogenase (RALDH)2, which is encoded by the aldehyde dehydrogenase 1 family, member A2 (ALDH1A2) gene and converts retinal to RA. IL-4 (4, 9) and TLR ligands (2,4,5,(10)(11)(12) augment the expression of RALDH2. These studies have presented a model that appropriately stimulated CD103 + DCs in gut-associated tissues produce RA and thus induce gut-homing Treg cells, resulting in maintaining immune homeostasis in the intestine in mice.…”

“…To quantify the activity of RALDH in mouse (2,4,5,7,8,12,19) and human (5,19) DCs, recent studies used the Aldefluor reagent that freely diffuses into cells and is converted to a fluorescent product by aldehyde dehydrogenase (ALDH) activity. Thus, we used this reagent in combination with quantitation of ALDH1A2 mRNA to quantify the RA-producing capacity of DCs.…”