Α-galactosylceramide analogs with weak agonist activity for human iNKT cells define new candidate anti-inflammatory agents.

CD1d-restricted natural killer T cells with invariant T cell receptor α chains (iNKT cells) are a unique lymphocyte subset that responds to recognition of specific lipid and glycolipid antigens. They are conserved between mice and humans and exert various immunoregulatory functions through their rapid secretion of a variety of cytokines and secondary activation of dendritic cells, B cells and NK cells. In the current study, we analyzed the range of functional activation states of human iNKT cells using a library of novel analogs of α-galactosylceramide (αGalCer), the prototypical iNKT cell antigen.

Recognition of lyso-phospholipids by human natural killer T lymphocytes.

Natural killer T (NKT) cells are a subset of T lymphocytes with potent immunoregulatory properties. Recognition of self-antigens presented by CD1d molecules is an important route of NKT cell activation; however, the molecular identity of specific autoantigens that stimulate human NKT cells remains unclear. Here, we have analyzed human NKT cell recognition of CD1d cellular ligands.

Kinetics and cellular site of glycolipid loading control the outcome of natural killer T cell activation.

CD1d-restricted natural killer T cells (NKT cells) possess a wide range of effector and regulatory activities that are related to their ability to secrete both T helper 1 (Th1) cell- and Th2 cell-type cytokines. We analyzed presentation of NKT cell activating alpha galactosylceramide (alphaGalCer) analogs that give predominantly Th2 cell-type cytokine responses to determine how ligand structure controls the outcome of NKT cell activation. Using a monoclonal antibody specific for alphaGalCer-CD1d complexes to visualize and quantitate glycolipid presentation, we found that Th2 cell-type cytokine-biasing ligands were characterized by rapid and direct loading of cell-surface CD1d proteins.

Natural killer T-cell autoreactivity leads to a specialized activation state.

Natural killer T (NKT) cells are innate-like T cells that recognize specific microbial antigens and also display autoreactivity to self-antigens. The nature of NKT-cell autoreactive activation remains poorly understood. We show here that the mitogen-activated protein kinase (MAPK) pathway is operative during human NKT-cell autoreactive activation, but calcium signaling is severely impaired.

Rapid identification of immunostimulatory alpha-galactosylceramides using synthetic combinatorial libraries.

Two 60+-membered libraries of alpha-galactosylceramides have been prepared by reactions between activated ester resins and two core, fully deprotected galactosylated sphingoid bases. The libraries were evaluated for their ability to stimulate CD1d-restricted NKT cells, using in vitro stimulation of a murine NKT cell hybridoma line and for their ability to induce the expansion of NKT cells from peripheral blood mononuclear cells (PBMC) of a normal human subject. Our results showed that many compounds constructed on a C18-phytosphingosine base had significant stimulatory activity in both assays.

Production and characterization of monoclonal antibodies against complexes of the NKT cell ligand alpha-galactosylceramide bound to mouse CD1d.

The alpha-galactosylceramide (alpha-GalCer) known as KRN7000 remains the best studied ligand of the lipid-binding MHC class I-like protein CD1d. The KRN7000:CD1d complex is highly recognized by invariant natural killer T (iNKT) cells, an evolutionarily conserved subset of T lymphocytes that express an unusual semi-invariant T cell antigen receptor, and mediate a variety of proinflammatory and immunoregulatory functions. To facilitate the study of glycolipid antigen presentation to iNKT cells by CD1d, we undertook the production of mouse monoclonal antibodies (mAbs) specific for complexes of KRN7000 bound to mouse CD1d (mCD1d) proteins.

Synthesis and evaluation of sphinganine analogues of KRN7000 and OCH.

[structures: see text] The phytosphingosine-containing alpha-galactosylceramides (alpha-GalCers), KRN7000 and OCH, have been shown to activate NKT cells via interaction with CD1d, a member of the CD1 family of antigen presenting proteins. Evidence from KRN7000 stimulation of NKT cells suggests that alpha-GalCers may have applications in the treatment or prevention of a range of viral, bacterial, and autoimmune conditions. Moreover, OCH, a truncated analogue of KRN7000, appears to induce a T(H)2 bias, which could have implications for the treatment of autoimmune and inflammatory conditions.

The T cell antigen receptor expressed by Valpha14i NKT cells has a unique mode of glycosphingolipid antigen recognition.

Natural killer (NK) T cells with an invariant Valpha14 rearrangement (Valpha14i) are the largest population of lipid antigen-specific T lymphocytes identified in animals. They react to the glycolipid alpha-galactosyl ceramide (alpha-GalCer) presented by CD1d, and they may have important regulatory functions. It was previously shown that the Valpha14i T cell antigen receptor (TCR) has a high affinity for the alpha-GalCer/CD1d complex, driven by a long half-life (t(1/2)).

Adsorption and detection of some phenolic compounds by rice husk ash of Kenyan origin.

Rice husk ash (RHA) obtained from a rice mill in Kenya has been used as an inexpensive and effective adsorbent (and reagent) for the removal (and detection) of some phenolic compounds in water. The abundantly available rice mill waste was used in dual laboratory-scale batch experiments to evaluate its potential in: (i) the removal of phenol, 1,3-dihydroxybenzene (resorcinol) and 2-chlorophenol from water; and (ii) the detection of 1,2-dihydroxybenzene (pyrocatechol) and 1,2,3-trihydroxybenzene (pyrogallol) present in an aqueous medium. The studies were conducted using synthetic water with different initial concentrations of the phenolic compounds.