Retinoic acid induction of CD1d expression primes chronic lymphocytic leukemia B cells for killing by CD8+ invariant natural killer T cells

Invariant natural killer T (iNKT) cells are cytotoxic T cells that respond to glycolipid antigens presented by CD1d. Therapeutic activation of iNKT cells with α-galactosylceramide (α-GalCer) can prevent and reverse tumor growth in mice and clinical trials involving α-GalCer-stimulated iNKT cells are ongoing in humans. B cells express CD1d, however, we show that CD1d expression is reduced on B cells from patients with chronic lymphocytic leukemia (CLL). B cells from CLL patients pulsed with α-GalCer failed to stimulate cytolytic degranulation by iNKT cell lines, but could present the more potent glycolipid analogue, 7DW8-5. Retinoic acid receptor-α (RAR-α) agonists induced CD1d expression by CLL B cells, restoring their ability to present α-GalCer to CD8α⁺ iNKT cells, resulting in cytolytic degranulation. Thus, RAR-α agonists can augment the anti-tumor activities of iNKT cells against CLL cells in vitro. Their inclusion in iNKT cell-based therapies may benefit patients with CLL.

Myeloid Engraftment in Humanized Mice: Impact of Granulocyte-Colony Stimulating Factor Treatment and Transgenic Mouse Strain

Poor myeloid engraftment remains a barrier to experimental use of humanized mice. Focusing primarily on peripheral blood cells, we compared the engraftment profile of NOD-scid-IL2Rγc(-/-) (NSG) mice with that of NSG mice transgenic for human membrane stem cell factor (hu-mSCF mice), NSG mice transgenic for human interleukin (IL)-3, granulocyte-macrophage-colony stimulating factor (GM-CSF), and stem cell factor (SGM3 mice). hu-mSCF and SGM3 mice showed enhanced engraftment of human leukocytes compared to NSG mice, and this was reflected in the number of human neutrophils and monocytes present in these strains. Importantly, discrete classical, intermediate, and nonclassical monocyte populations were identifiable in the blood of NSG and hu-mSCF mice, while the nonclassical population was absent in the blood of SGM3 mice. Granulocyte-colony stimulating factor (GCSF) treatment increased the number of blood monocytes in NSG and hu-mSCF mice, and neutrophils in NSG and SGM3 mice; however, this effect appeared to be at least partially dependent on the stem cell donor used to engraft the mice. Furthermore, GCSF treatment resulted in a preferential expansion of nonclassical monocytes in both NSG and hu-mSCF mice. Human tubulointerstitial CD11c(+) cells were present in the kidneys of hu-mSCF mice, while monocytes and neutrophils were identified in the liver of all strains. Bone marrow-derived macrophages prepared from NSG mice were most effective at phagocytosing polystyrene beads. In conclusion, hu-mSCF mice provide the best environment for the generation of human myeloid cells, with GCSF treatment further enhancing peripheral blood human monocyte cell numbers in this strain.

Human Natural Killer cell expression of ULBP2 is associated with a mature functional phenotype

NKG2D is an important activating receptor expressed on NK cells. Ligands (termed NKG2DL) for this receptor include ULBP1-6, MICA and MICB in humans; they are upregulated in stressed, cancerous or infected cells where they engage NKG2D to induce NK cell cytotoxicity and cytokine production. Expression of NKG2DL on effector cells has been described in mice and more recently in human cells. We confirm that NK cell lines and IL-2 stimulated primary human NK cells also express the NKG2DL, ULBP2. However, expression of ULBP2 was not a result of transfer from a non-NK cell to an NK cell and in contrast to recent reports we saw no evidence that ULBP2 expression targeted these NK cells for fratricide or for cytotoxicity by NKG2D-expressing, non-NK effector cells. ULBP2 expression was however linked to expression of mature CD57(+) NK cells. In particular, expression of ULBP2 was strongest on those NK cells that had evidence of recent activation and proliferation. We suggest that ULBP2 could be used to identify recently activated "mature" NK cells. Defining this phenotype would be useful for understanding the ontogeny on human NK cells.

Urinary Soluble CD163 in Active Renal Vasculitis

A specific biomarker that can separate active renal vasculitis from other causes of renal dysfunction is lacking, with a kidney biopsy often being required. Soluble CD163 (sCD163), shed by monocytes and macrophages, has been reported as a potential biomarker in diseases associated with excessive macrophage activation. Thus, we hypothesized that urinary sCD163 shed by crescent macrophages correlates with active glomerular inflammation. We detected sCD163 in rat urine early in the disease course of experimental vasculitis. Moreover, microdissected glomeruli from patients with small vessel vasculitis (SVV) had markedly higher levels of CD163 mRNA than did those from patients with lupus nephritis, diabetic nephropathy, or nephrotic syndrome. Both glomeruli and interstitium of patients with SVV strongly expressed CD163 protein. In 479 individuals, including patients with SVV, disease controls, and healthy controls, serum levels of sCD163 did not differ between the groups. However, in an inception cohort, including 177 patients with SVV, patients with active renal vasculitis had markedly higher urinary sCD163 levels than did patients in remission, disease controls, or healthy controls. Analyses in both internal and external validation cohorts confirmed these results. Setting a derived optimum cutoff for urinary sCD163 of 0.3 ng/mmol creatinine for detection of active renal vasculitis resulted in a sensitivity of 83%, specificity of 96%, and a positive likelihood ratio of 20.8. These data indicate that urinary sCD163 level associates very tightly with active renal vasculitis, and assessing this level may be a noninvasive method for diagnosing renal flare in the setting of a known diagnosis of SVV.

Intermediate monocytes in ANCA vasculitis: increased surface expression of ANCA autoantigens and IL-1β secretion in response to anti-MPO antibodies

ANCA vasculitis encompasses several autoimmune conditions characterised by destruction of small vessels, inflammation of the respiratory tract and glomerulonephritis. Most patients harbour autoantibodies to myeloperoxidase (MPO) or proteinase 3 (PR3). Clinical and experimental data suggest that pathogenesis is driven by ANCA-mediated activation of neutrophils and monocytes. We investigated a potential role for distinct monocyte subsets. We found that the relative proportion of intermediate monocytes is increased in patients versus control individuals, and both MPO and PR3 are preferentially expressed on these cells. We demonstrate that MPO and PR3 are expressed independently of each other on monocytes and that PR3 is not associated with CD177. MPO expression correlates with that of Fc receptor CD16 on intermediate monocytes. Monocyte subsets respond differently to antibodies directed against MPO and PR3, with anti-MPO but not anti-PR3 leading to increased IL-1β, IL-6 and IL-8 production. In concordance with the observed higher surface expression of MPO on intermediate monocytes, this subset produces the highest quantity of IL-1β in response to anti-MPO stimulation. These data suggest that monocytes, specifically, the intermediate subset, may play a role in ANCA vasculitis, and also indicate that substantial differences exist between the effect of anti-MPO and anti-PR3 antibodies on these cells.

Human invariant NKT cell subsets differentially promote differentiation, antibody production, and T cell stimulation by B cells in vitro

Invariant NK T (iNKT) cells can provide help for B cell activation and Ab production. Because B cells are also capable of cytokine production, Ag presentation, and T cell activation, we hypothesized that iNKT cells will also influence these activities. Furthermore, subsets of iNKT cells based on CD4 and CD8 expression that have distinct functional activities may differentially affect B cell functions. We investigated the effects of coculturing expanded human CD4(+), CD8α(+), and CD4(-)CD8α(-) double-negative (DN) iNKT cells with autologous peripheral B cells in vitro. All iNKT cell subsets induced IgM, IgA, and IgG release by B cells without needing the iNKT cell agonist ligand α-galactosylceramide. Additionally, CD4(+) iNKT cells induced expansions of cells with phenotypes of regulatory B cells. When cocultured with α-galactosylceramide-pulsed B cells, CD4(+) and DN iNKT cells secreted Th1 and Th2 cytokines but at 10-1000-fold lower levels than when cultured with dendritic cells. CD4(+) iNKT cells reciprocally induced IL-4 and IL-10 production by B cells. DN iNKT cells expressed the cytotoxic degranulation marker CD107a upon exposure to B cells. Remarkably, whereas iNKT cell subsets could induce CD40 and CD86 expression by B cells, iNKT cell-matured B cells were unable to drive proliferation of autologous and alloreactive conventional T cells, as seen with B cells cultured in the absence of iNKT cells. Therefore, human CD4(+), CD8α(+), and DN iNKT cells can differentially promote and regulate the induction of Ab and T cell responses by B cells.

Cutting edge: CD1d restriction and Th1/Th2/Th17 cytokine secretion by human Vδ3 T cells

Human γδ T cells expressing the Vδ3 TCR make up a minor lymphocyte subset in blood but are enriched in liver and in patients with some chronic viral infections and leukemias. We analyzed the frequencies, phenotypes, restriction elements, and functions of fresh and expanded peripheral blood Vδ3 T cells. Vδ3 T cells accounted for ~0.2% of circulating T cells, included CD4(+), CD8(+), and CD4(-)CD8(-) subsets, and variably expressed CD56, CD161, HLA-DR, and NKG2D but neither NKG2A nor NKG2C. Vδ3 T cells were sorted and expanded by mitogen stimulation in the presence of IL-2. Expanded Vδ3 T cells recognized CD1d but not CD1a, CD1b, or CD1c. Upon activation, they killed CD1d(+) target cells, released Th1, Th2, and Th17 cytokines, and induced maturation of dendritic cells into APCs. Thus, Vδ3 T cells are glycolipid-reactive T cells with distinct Ag specificities but functional similarities to NKT cells.