IgG antibodies can suppress more than 99% of the antibody response against the antigen to which they bind. This is used clinically to prevent rhesus-negative (Rh ؊ ) women from becoming immunized against Rh ؉ erythrocytes from their fetuses. The suppressive mechanism is poorly understood, but it has been proposed that IgG͞erythrocyte complexes bind to the inhibitory

Background:The enzyme myeloperoxidase produces chlorine bleach at sites of inflammation. Results: 2-Thioxanthines are potent mechanism-based inactivators of myeloperoxidase. Conclusion: 2-Thioxanthines block production of chlorine bleach during inflammation. Significance: Mechanism-based inactivators of myeloperoxidase should limit oxidative stress at sites of inflammation.

The ability of antigen-specific IgE antibodies to modulate the in vivo antibody response was studied by comparing the antibody response in mice immunized with 2,4,6-trinitrophenyl (TNP)-specific monoclonal IgE followed by bovine serum albumin (BSA)-TNP or with BSA-TNP alone. The serum IgG antibody response against BSA, measured in enzyme-linked immunosorbent assay ELISA, was enhanced up to 100-fold in groups receiving IgE. The enhancement required specific interaction between IgE and antigen, since no effect was seen when unconjugated BSA was used as antigen. Polyclonal activation by IgE/antigen complexes did not occur. IgE given 24 h after specific antigen had no stimulatory capacity. Pretreatment of the mice with Fc epsilon receptor type II (Fc epsilon RII)-specific monoclonal antibody completely inhibited the IgE-mediated enhancement. Thus, the data demonstrate for the first time an in vivo role for Fc epsilon RII in enhancement of specific antibody production.

No abstract

Although not endogenous in nature, the sulfonamide functionality is widely found in organic molecules with biological activity. A search of Thomson Reuters Integrity reveals that the sulfonamide motif appears in 111 approved drugs or agents in clinical trials, [1] and the total number of organic molecules containing this functional group is enormous. In contrast, the sulfonamide isostere [2] in which one of the sulfonamide oxygen atoms have been replaced by a nitrogen atom, thus creating a sulfonimidamide has received little attention in the literature. The first reports on sulfonimidamides were published in the early 1960s, [3] however, it was only during the last few years that the research groups of Malacria [4] and Dodd [5] explored the use of sulfonimidamides as reagents in organic synthesis, while Bolm et al. explored sulfonimidamides as chiral organocatalysts [6a] and as ligands for transition metal-catalyzed asymmetric synthesis.[6b]

Mice immunized with IgE/Ag complexes produce significantly more Ag-specific Abs than mice immunized with Ag alone. The enhancement is mediated via the low-affinity receptor for IgE (FcεRII or CD23), as shown by its complete absence in mice pretreated with mAbs specific for CD23 and in CD23-deficient mice. Because the constitutive expression of murine CD23 is limited to B cells and follicular dendritic cells (FDCs), one of these cell types is likely to be involved. One of the suggested modes of action of IgE/CD23 is to increase the ability of B cells to present Ag to T cells, as demonstrated to take place in vitro. Another possibility is that FDCs capture the IgE/Ag complexes and present these directly to B cells. The purpose of the present study was to determine whether CD23+ B cells or FDCs are responsible for the IgE/CD23-mediated enhancement of specific Ab responses in vivo. We show that the enhancement is completely restored in irradiated CD23-deficient mice reconstituted with CD23+ spleen or bone marrow cells. In these mice, the B cells are CD23+ and the FDCs are presumably CD23− because the FDCs are radiation resistant and are reported not to be replaced by donor cells after this type of cell transfer. In contrast, enhancement was not restored in irradiated wild-type mice reconstituted with CD23− cells. These results indicate that CD23+ B cells, and not FDCs, are the cells that capture IgE/Ag complexes and induce enhancement of Ab responses in vivo.

No abstract

␥-Secretase inhibition represents a major therapeutic strategy for lowering amyloid ␤ (A␤) peptide production in Alzheimer's disease (AD).Progress toward clinical use of ␥-secretase inhibitors has, however, been hampered due to mechanism-based adverse events, primarily related to impairment of Notch signaling. The ␥-secretase inhibitor MRK-560 represents an exception as it is largely tolerable in vivo despite displaying only a small selectivity between A␤ production and Notch signaling in vitro. In exploring the molecular basis for the observed tolerability, we show that MRK-560 displays a strong preference for the presenilin 1 (PS1) over PS2 subclass of ␥-secretases and is tolerable in wild-type mice but causes dose-dependent Notch-related side effect in PS2-deficient mice at drug exposure levels resulting in a substantial decrease in brain A␤ levels. This demonstrates that PS2 plays an important role in mediating essential Notch signaling in several peripheral organs during pharmacological inhibition of PS1 and provide preclinical in vivo proof of concept for PS2-sparing inhibition as a novel, tolerable and efficacious ␥-secretase targeting strategy for AD.