Takayuki Sato

Physical linkage of a variable region segment and the joining region segment of the human immunoglobulin heavy chain locus

We have isolated overlapping cosmid clones containing both human VH-VI and D gene segments from genomic libraries of a human lymphocyte line which has the germline context of the immunoglobulin loci. Characterization of the cosmid clones revealed that the VH-VI gene was located about 20 kb upstream to the D4 segment with the same transcriptional orientation relative to the D and JH segments. No other VH genes were found downstream to the VH-VI gene using VH probes hybridizing all the six human VH families so far identified. The results indicate that the VH-VI gene is the most proximal VH segments among the known VH family members and that the distance between the VH and JH segments is not longer than 70 kb in the human genome.

The tyrosine kinase inhibitor dasatinib suppresses cytokine production by plasmacytoid dendritic cells by targeting endosomal transport of CpG DNA

Plasmacytoid dendritic cells (pDCs) produce a vast amount of interferon (IFN)‐α in response to nucleic acids from viruses and damaged self‐cells through Toll‐like receptor (TLR)7 and TLR9. Pharmaceutical agents that suppress IFN‐α production by pDCs are instrumental in elucidating the mechanisms behind IFN‐α production, and in developing novel therapies for inflammatory disorders that involve pDCs. Here, we show that a tyrosine kinase inhibitor for chronic myeloid leukemia with multiple targets, dasatinib, strongly suppresses production of IFN‐α and proinflammatory cytokines by human pDCs stimulated with multimeric CpG oligodeoxynucleotides (CpG‐A) without reducing viability. In contrast, other tyrosine kinase inhibitors, imatinib, and nilotinib, did not suppress the cytokine production at clinically relevant concentrations. Inhibitors of SRC family kinases (SFKs), which are prominent targets of dasatinib, also suppressed the cytokine production. Notably, however, dasatinib, but not SFK inhibitors, abrogated prolonged localization of CpG‐A in early endosomes, which is a critical step for pDCs to produce a large amount of IFN‐α. This study suggests that dasatinib suppresses IFN‐α production by pDCs by inhibiting SFK‐dependent pathways and SFK‐independent endosomal retention of CpG DNA. Kinases controlling the distinctive endosomal trafficking in pDCs may be exploited as targets to develop novel therapies for pDC‐related inflammatory disorders.

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

All-trans-retinoic acid (RA) plays a critical role in maintaining immune homeostasis. Mouse intestinal CD103+ dendritic cells (DCs) produce a high level of RA by highly expressing retinal dehydrogenase (RALDH)2, an enzyme that converts retinal to RA, and induce gut-homing T cells. However, it has not been identified which subset of human DCs produce a high level of RA. In this study, we show that CD1c+ blood myeloid DCs (mDCs) but not CD141high mDCs or plasmacytoid DCs exhibited a high level of RALDH2 mRNA and aldehyde dehydrogenase (ALDH) activity in an RA- and p38-dependent manner when stimulated with 1α,25-dihydroxyvitamin D3 (VD3) in the presence of GM-CSF. The ALDH activity was abrogated by TLR ligands or TNF. CD103− rather than CD103+ human mesenteric lymph node mDCs gained ALDH activity in response to VD3. Furthermore, unlike in humans, mouse conventional DCs in the spleen and mesenteric lymph nodes gained ALDH activity in response to GM-CSF alone. RALDH2high CD1c+ mDCs stimulated naive CD4+ T cells to express gut-homing molecules and to produce Th2 cytokines in an RA-dependent manner. This study suggests that CD1c+ mDCs are a major human DC subset that produces RA in response to VD3 in the steady state. The “vitamin D – CD1c+ mDC – RA” axis may constitute an important immune component for maintaining tissue homeostasis in humans.

Clinical significance of subcategory and severity of chronic graft-versus-host disease evaluated by National Institutes of Health consensus criteria.

To evaluate the clinical significance of subcategory and severity of chronic graft-versus-host disease (GVHD) as defined by the National Institutes of Health (NIH) consensus criteria, we retrospectively studied 211 patients with hematologic neoplasms who survived beyond 100 days after allogeneic hematopoietic cell transplantation. Endpoints included chronic GVHD-specific survival (cGSS), duration of immunosuppressive treatment, and non-relapse mortality (NRM). A total of 96 patients fulfilled the NIH diagnostic criteria for cGVHD. In univariable analysis, patients with NIH overlap syndrome tended to exhibit lower cGSS compared to those with NIH classic cGVHD [hazard ratio (HR) = 2.76, P = 0.060], while patients with severe cGVHD at onset had a significantly lower cGSS compared to those with mild-to-moderate cGVHD (HR = 3.10, P = 0.034). The duration of immunosuppressive treatment was not significantly affected by either subcategory or severity of NIH cGVHD. In multivariable analysis treating cGVHD as a time-dependent covariate, development of overlap syndrome (HR = 3.90, P = 0.014) or severe cGVHD at peak worsening (HR = 6.21, P < 0.001) was significantly associated with higher risk of NRM compared to the absence of cGVHD. Our results suggest that both the subcategory and severity of NIH cGVHD are partly correlated with cGSS and may play a useful role in distinguishing patients at high risk for NRM, warranting validation of this approach through future prospective studies.