Subset In Lymph Nodes Research Articles

Plasmacytoid dendritic cells suppress Th2 responses induced by epicutaneous sensitization.

Epicutaneous (EC) sensitization with protein allergens is the most important sensitization route for atopic dermatitis. Plasmacytoid dendritic cells (pDCs) are characterized by massive secretion of interferon-α (IFNα). B6 mice are T helper type 1 (Th1)-prone and are representative of non-atopic humans, whereas BALB/c mice are Th2-prone and are representative of atopic humans. Here, we show that naïve BALB/c mice contain a greater number of nonactivated pDCs in peripheral lymph nodes (LNs) than do naïve B6 mice. Naïve BALB/c mice also have more of the CD8α- subset in LNs than naïve B6 mice. Moreover, in vivo depletion of pDCs during EC sensitization results in enhanced Th2 responses in BALB/c mice, but not in B6 mice. Mechanistically, when BALB/c mice undergo EC sensitization, there is an increase in pDCs entering draining LNs. These cells exhibit modest activation including comparable costimulation expression but increased cytokine expression compared with those of naïve mice. In vivo depletion of pDCs during EC sensitization significantly increases the activation of dermal dendritic cells (dDCs) suggesting a regulatory effect on these cells. To this end, a suppressive effect of pDCs on conventional dendritic cells was also demonstrated in vitro. Further, in vivo blockade of IFNα by an anti-IFNAR antibody (Ab) or in vivo reduction of IFNα production of pDCs by anti-siglec-H Ab both resulted in enhanced activation of dDCs. Collectively, our results demonstrate that pDCs suppress Th2 responses induced by EC sensitization via IFNα-mediated regulation of dDCs.

Dendritic Cells Display Subset and Tissue-Specific Maturation Dynamics over Human Life

Maturation and migration to lymph nodes (LNs) constitutes a central paradigm in conventional dendritic cell (cDC) biology but remains poorly defined in humans. Using our organ donor tissue resource, we analyzed cDC subset distribution, maturation, and migration in mucosal tissues (lungs, intestines), associated lymph nodes (LNs), and other lymphoid sites from 78 individuals ranging from less than 1 year to 93 years of age. The distribution of cDC1 (CD141hiCD13hi) and cDC2 (Sirp-α+CD1c+) subsets was a function of tissue site and was conserved between donors. We identified cDC2 as the major mature (HLA-DRhi) subset in LNs with the highest frequency in lung-draining LNs. Mature cDC2 in mucosal-draining LNs expressed tissue-specific markers derived from the paired mucosal site, reflecting their tissue-migratory origin. These distribution and maturation patterns were largely maintained throughout life, with site-specific variations. Our findings provide evidence for localized DC tissue surveillance and reveal a lifelong division of labor between DC subsets, with cDC2 functioning as guardians of the mucosa.

Analysis of Micrometastatic Disease in Sentinel Lymph Nodes From Resectable Colon Cancer: Results of Cancer and Leukemia Group B Trial 80001

To determine whether sentinel lymph node (LN) sampling (SLNS) could reduce the number of nodes required to characterize micrometastatic disease (MMD) in patients with potentially curable colon cancer. Cancer and Leukemia Group B 80001 was a study to determine whether SLNS could identify a subset of LNs that predicted the status of the nodal basin for resectable colon cancer and, therefore, could be extensively evaluated for the presence of micrometastases. Patients enrolled onto this study underwent SLNS after injection of 1% isosulfan blue, and both sentinel nodes (SNs) and non-SNs obtained during primary tumor resection were sectioned at multiple levels and stained using anti-carcinoembryonic antigen and anticytokeratin antibodies. Using standard histopathology, SNs failed to predict the presence of nodal disease in 13 (54%) of 24 node-positive patients. Immunostains were performed for patients whose LNs were negative by standard histopathology. Depending on the immunohistochemical criteria used to assign LN positivity, SN examination resulted in either an unacceptably high false-positive rate (20%) or a low sensitivity for detection of MMD (40%). By examining both SNs and non-SNs, this multi-institutional study showed that SNs did not accurately predict the presence of either conventionally defined nodal metastases or MMD. As a result, SLNS is not a useful technique for the study of MMD in patients with colon cancer.

A Novel Human CD34(+) Subset That Constitutively Expresses the High Affinity Interleukin-2 Receptor Traffics to Lymph Nodes and Differentiates into CD56Bright Natural Killer Cells.

In adult humans, T cells differentiate in the thymus and B cells develop in the bone marrow, but the site(s) of natural killer (NK) cell differentiation are unclear. Here we describe, for the first time, a unique CD34(+) population found in human lymph nodes (LN) that differentiates into NK cells. CD56bright NK cells represent <10% of NK cells in peripheral blood (PB) yet predominate in LN where they can compete for endogenous T cell-derived IL-2 during immune activation due to their unique expression of functional high affinity (HA) interleukin (IL)-2 receptors (IL-2R). We hypothesized that a subset of CD34(+) hematopoietic precursor cells (HPC) might also express functional HA IL-2R and potentially differentiate into CD56bright NK cells via activation with low dose IL-2. We first identified a novel human CD34dimCD45RA(+) HPC in PB with constitutive expression of the HA IL-2R. When cultured in picomolar concentrations of IL-2 that selectively saturate the HA IL-2R, these cells give rise to CD56bright NK cells, and this effect is blocked when IL-2 cannot bind to its HA receptor. This unique CD34(+) population expresses IL-2Rα, CD2, CD7, c-kit, L-selectin, and NKR-P1A, all of which are also expressed by CD56bright NK cells. Unique among total PB CD34(+) cells, this novel population displays high integrin α4β7 expression. This attribute, in addition to its high L-selectin expression, suggested that these cells may traffic to LN where their progeny, CD56bright NK cells, represent the major NK subset. Indeed we found a distinct CD34dimCD45RA(+)α4β7bright population that resides in the T cell rich regions of human LN, and when stimulated in vitro with 10 pM IL-2, this cell gives rise to CD56bright NK cells. This novel population represents only ~6% of all PB CD34(+) HPC yet is the major if not exclusive CD34(+) subset in LN. While murine studies strongly support the notion that most if not all NK cells require IL-15 for their development, these new human data suggest a model for development of a minor human NK subset, the CD56bright NK cells, whereby CD34dimCD45RA(+)α4β7bright HPC constitutively expressing the HA IL-2R traffic to peripheral LN where endogenous T cell-derived IL-2 can drive CD56bright NK cell differentiation in vivo.

Selection of intestinal intraepithelial lymphocyte T cell receptors: evidence for a dynamic tissue-specific process.

An extensive comparison of TCR alpha beta V-region usage by CD8 beta-CD4+CD8+ intraepithelial lymphocytes (IEL), CD4-CD8+ IEL, and lymph node (LN) T cell subsets in three minor lymphocyte stimulating (Mls)-disparate, MHC-identical mouse strains revealed novel TCR selection patterns. In cases where forbidden V regions were expressed by CD8 beta- CD4-CD8+ IEL, the same TCRs were deleted from CD8 beta- CD4+CD8+ IEL, indicating that lack of CD8 beta expression was not solely responsible for forbidden V-region expression. These results also suggested that CD4 may be involved in negative selection of CD4+CD8+ IEL TCRs. In C57BR/cdJ (Mls-1b2b) mice, a major increase in V beta 3+CD4+CD8+ IEL but not in other IEL or LN subsets was noted suggesting a subset-specific expansion of V beta 3+ cells. Negative selection of V beta 14+ cells in only the CD4+CD8+ IEL subset further supported the existence of intestine-specific TCR selection processes. Analysis of V-region expression of CD8 beta + and CD8 beta-CD4-CD8+ IEL subsets revealed that forbidden V-region expression was not strictly confined to the CD8 beta- subset in all cases. Overall, the data point to a dynamic, gut-specific TCR selection process that may be antigen driven.