No abstract

Receptors for IgG Abs (Fcγ receptors) are capable of triggering diverse cell responses in leukocytes. In neutrophils, two Fcγ receptors, namely FcγRIIA and FcγRIIIB, are constitutively expressed. The signaling pathways that regulate FcγRIIA-mediated phagocytosis have been relatively well described. However, the different signaling pathways that lead to NF activation after engagement of each Fcγ receptor have only been partially described. To address this problem, neutrophils were stimulated by cross-linking selectively each type of Fcγ receptor with specific mAbs, and NF activation was then analyzed. FcγRIIIB, but not FcγRIIA, promoted a robust increase in phosphorylated ERK in the nucleus, and also efficient phosphorylation of the NF Elk-1. Complete mAb 3G8 (anti-FcγRIIIB) induced a higher response than did F(ab′)2 fragments of mAb 3G8, suggesting a possible synergistic effect of both FcγR receptors. However, mAb IV.3 (anti-FcγRIIA) alone did not cause an increase of phosphorylated ERK in the nucleus. FcγRIIIB-induced nuclear phosphorylation of ERK, and of Elk-1, was not affected by Syk, PI3K, or MEK inhibitors. In contrast, FcγRIIA- or FcγRIIIB-mediated phosphorylation of cytoplasmic ERK depended on Syk, PI3K, and MEK. Also, ERK, but not MEK, was constitutively present in the nucleus, and FcγRIIIB cross-linking did not increase the levels of nuclear ERK or MEK. These data clearly show that different neutrophil Fcγ receptors possess different signaling capabilities. FcγRIIIB, but not FcγRIIA, activates a unique signaling pathway leading to the nuclear-restricted phosphorylation of ERK and Elk-1, independently of Syk, PI3K, or MEK.

Hybrid bionanocomposites based on cellulose matrix, with silica nanoparticles as reinforcers, were prepared by one-pot synthesis of cellulose surface modified by solvent exchange method to keep the biopolymer net void for hosting inorganic nanoparticles. Neither expensive inorganic-particle precursors nor crosslinker agents or catalysts were used for effective dispersion of reinforcer concentration up to 50 wt %. Scanning electron microscopy of the nanocomposites shows homogeneous dispersion of reinforcers in the surface modified cellulose matrix. The FTIR spectra demonstrated the cellulose features even at 50 weight percent content of silica nanoparticles. Such a high content of silica provides high thermal stability to composites, as seen by TGA-DSC. The fungi decay resistance to Trametes versicolor was measured by standard test showing good resistance even with no addition of antifungal agents. This one-pot synthesis of biobased hybrid materials represents an excellent way for industrial production of high performance materials, with a high content of inorganic nanoparticles, for a wide variety of applications.