Phytochemical and immunomodulatory properties of an Echinacea laevigata (Asteraceae) tincture.

Background: Echinacea preparations are consumed for the prevention or treatment of upper respiratory infections.

Objective: The objective of this study was to provide the first data regarding the in vitro immunomodulatory properties of the American federally endangered species Echinacea laevigata (Asteraceae).

Methods: Human peripheral blood mononuclear cells were cultured with root tinctures from E.

Retinoic acid-induced protein ISGylation is dependent on interferon signal transduction.

Interferon-stimulated gene 15 (ISG15) is a ubiquitin-like modifier that forms conjugates with target protein substrates. As its name suggests, its expression and conjugation to other proteins are highly regulated by interferon (IFN). It was recently demonstrated that ISG15 expression, ISG15 conjugation, and several enzymes involved in ISG15 modification are upregulated in an acute promyelocytic cell line following treatment with retinoic acid, suggesting a possible retinoic acid induced IFN-independent ISG15 modification pathway.

ISG15: a ubiquitin-like enigma.

ISG15 is a 17 kDa protein encoded by an interferon stimulated gene. Described in 1979, it was the first ubiquitin-like modifier to be identified, and its discovery followed the first reports of ubiquitin by only four years. While many important functions for ubiquitin have been reported, the functions for ISG15 and its conjugation are still largely unknown.

A novel single chain I-A(b) molecule can stimulate and stain antigen-specific T cells.

Multimers of soluble major histocompatibility complex class I and II molecules have proven to be useful reagents in quantifying and following specific T cell populations. This study describes the design, generation, and characterization of a novel, single chain I-A(b) molecule which utilizes a unique linker derived from the murine invariant chain. A fragment of the invariant chain, residues 58-85, binds to a region proximal to the class II peptide binding groove and stabilizes occupancy of the class II invariant chain-associated peptide.

Analysis of two acidic P6 pocket residues in the pH dependency of peptide binding by I-E(k).

Peptide binding to major histocompatibility complex (MHC) class II molecules is optimal at mildly acidic pH. X-ray crystal structures solved for the murine class II molecule I-E(k) revealed an interesting localization of negatively charged residues within the P6 pocket, which may have implications in the pH dependency of peptide binding. Protonation of these critical residues, under acidic conditions, has been proposed to be important for the formation of stable class II-peptide complexes.