Natural killer cells: Stop, look, listen

On how NK cells balance activating and inhibitory ligands in target cells to decide when to attack.

When a migratory natural killer (NK) cell encounters a potential target cell, it must stop and integrate signals from various sensory inputs to decide whether to proceed with a cytolytic response. Daniel Davis and colleagues show how the formation of a lytic synapse between an NK cell and a target cell, resulting in the polarized secretion of cytolytic granules, is continuously regulated by the balance between signalling through activating and inhibitory receptors.
[from Nature Reviews Immunology 9, 606, September 2009]

Comments from this interesting article:
Natural Killer Cell Signal Integration Balances Synapse Symmetry and Migration. Culley FJ, Johnson M, Evans JH, Kumar S, Crilly R, et al. 2009 PLoS Biol 7(7): e1000159. doi:10.1371/journal.pbio.1000159

  R&D Systems reagents used in that study:

• Antibodies to NKG2D (Clone 149810), NKG2A (clone 131411)
• Recombinant ICAM-1, ICAM-1-Fc and MICA-Fc chimeras
• IFNγ ELISA
  

Cancer stem cells news

Cancer Stem Cells (or 'tumor-initiating cells') are in the news again, this time with promising research on potential therapeutics (see NYTimes article here)

A team of scientists including Eric Lander, Robert Weinberg and Charlotte Kuperwasser identified selective inhibitors of Cancer Stem Cells by high-throughput screening (Gupta et al., Cell, August 13 2009) . 32 of the 16,000 chemicals screened selectively went after cancer stem cells.

Scientists from OncoMed Pharmaceuticals, a company dedicated to develop cancer therapies by targeting tumor-initiating cells, published an article in Cell Stem Cell demonstrating anti-cancer activity of a DLL4 blocking antibody in colon and breast cancer models (1). The antibody, the company’s first product candidate, OMP-21M18, is currently in Phase 1 clinical testing.

As we mentioned earlier in this post, blocking monoclonal antibodies directed against CD47 preferentially enabled phagocytosis of acute myeloid leukemia stem cells and inhibited their engraftment in vivo, making CD47 a potential therapeutic target for AML.
The same team led by Irv Weissman has now identified the first human bladder cancer stem cell, and has shown CD47 here again as a key player in allowing cancer cells to escape the body’s natural defenses (Chan et al., PNAS, June 28 2009).

Richard Lock and colleagues have also shown evidence of the elimination of human acute myeloid leukemic stem cells, this time by monoclonal antibody-mediated targeting of CD123, the IL-3 Receptor alpha Chain (Jin et al., Cell Stem Cell (5) 1, July 2009) .

(1) Recombinant human DLL4 from R&D Systems was used in the DLL4 study

	DLL4 products from R&D Systems
	CD47 products from R&D Systems
	IL-3R alpha (CD123) products from R&D Systems

CD47 expression in Leukemia Stem Cells

Expression of the cell-surface protein CD47 allows some normal cells to avoid phagocytosis by macrophages. Two articles in the July 23 issue of Cell from Irving Weissman's Lab at Stanford University show that elevated CD47 expression by leukemic stem cells inhibits macrophage activity and is an indicator of poor prognosis for patients with acute myeloid leukemia.

CD47 Is Upregulated on Circulating Hematopoietic Stem Cells and Leukemia Cells to Avoid Phagocytosis, Jaiswal et al. Cell 138 (2), 271-285 (2009)

CD47 Is an Adverse Prognostic Factor and Therapeutic Antibody Target on Human Acute Myeloid Leukemia Stem Cells, Majeti et al. Cell, 138 (2), 286-299 (2009)

Click here for a list of CD47 products from R&D Systems
	Human lymphocytes were stained with PE-conjugated anti-human CD47 (Catalog # FAB4670P, red histogram) or isotype control (Catalog #IC002P, open histogram).

Development and Characterization of a Novel Monoclonal Antibody to Human IL-17A

Download the poster in hi-res pdf format

Although IL-17A is made by CD4+ Th17 cells and there is an ever-increasing body of literature on these cells, other cells make IL-17A, including CD8+ (Tc17) and g-d T cells, NK cells, and neutrophils. There are many factors that contribute to published findings of the percentage of cells producing IL-17A, including the activation or differentiation conditions, time course of activation, and antibody used for detection. It has been published that high levels of IL-17A are secreted by human PBMCs after anti-CD3/CD28-treatment alone for only 24 hrs. We have developed a new monoclonal antibody (Clone 41802) that is specific for human IL-17A. The specificity of this Ab has been rigorously tested. Clone 41802 detects an increase in IL-17A in PMA/ionomycin-treated human PBMCs over resting cells by intracellular flow cytometry. This finding correlated with Western blot data in Th17-differentiated vs resting CD4+ PBMCs. This clone also detects IL-17A in a population of activated CD3+ PBMCs that is also positive for IL-22 and IL-23 R by flow cytometry. Importantly, clone 41802 detects IL-17A in transfectant cells overexpressing human IL-17A, but not in cells overexpressing human IL-17F. In conclusion, clone 41802 is specific for human IL-17A. Although a larger percentage of IL-17A+ cells are detected in activated PBMCs than with other commercially available clones, this indicates an interesting biological finding, not a lack of antibody specificity.