Measurement of polyclonal immunoglobulin synthesis using ELISA

The mammalian tRNA ligase complex mediates splicing of XBP1 mRNA and controls antibody secretion in plasma cells

The unfolded protein response (UPR) is a conserved stress-signaling pathway activated after accumulation of unfolded proteins within the endoplasmic reticulum (ER). Active UPR signaling leads to unconventional, enzymatic splicing of XBP1 mRNA enabling expression of the transcription factor XBP1s to control ER homeostasis. While IRE1 has been identified as the endoribonuclease required for cleavage of this mRNA, the corresponding ligase in mammalian cells has remained elusive. Here, we report that RTCB, the catalytic subunit of the tRNA ligase complex, and its co-factor archease mediate XBP1 mRNA splicing both in vitro and in vivo. Depletion of RTCB in plasma cells of Rtcb(fl/fl) Cd23-Cre mice prevents XBP1s expression, which normally is strongly induced during plasma cell development. RTCB-depleted plasma cells show reduced and disorganized ER structures as well as severe defects in antibody secretion. Targeting RTCB and/or archease thus represents a promising strategy for the treatment of a growing number of diseases associated with elevated expression of XBP1s.

The immunosuppressive activity of Ascaris suum is due to high molecular weight components

The role of isolated components obtained by gel filtration chromatography of Ascaris suum body extract (Asc) on the modulation of the immune response to ovalbumin (OvA) was evaluated and correlated with the immunogenic properties of such components. We showed that high (PI), but not low (PIII), molecular weight components have the ability to inhibit OvA-induced immediate and DTH reactions, lymph node (LN) cell proliferation, cytokine (IL-2, interferon-gamma (IFN-gamma), IL-4 and IL-10) and antibody (IgG1, IgG2a, IgM and IgE) production in mice concomitantly immunized with OvA and these high mol. wt components. The pattern of cytokines synthesized in response to PI or PIII was totally different: the former induced more IL-4 and IL-10 and the latter more IL-2 and IFN-gamma. The levels of Asc-specific IgG1 antibodies were higher in mice immunized with OvA plus PI and IgG2a anti-Asc antibodies predominated in those immunized with PIII. IgE antibody production, however, was low in the former group of mice. These results indicate that the high mol. wt components present in the body extract from the helminth A. suum are responsible for its suppressive effect upon Th1- and Th2-dependent immune responses to an unrelated antigen. The suppression of the Th1-dependent parameters could be related to high-level expression of IL-4 and IL-10 induced by such components.

Immunomodulation induced by Ascaris suum extract in mice: effect of anti-interleukin-4 and anti-interleukin-10 antibodies

Simultaneous immunization of mice with an Ascaris suum extract (Asc) and ovalbumin (OA) markedly affects the immune response to OA. The role of interleukin (IL)-4 and IL-10 induced by Asc immunization on the modulation of antigen-specific and mitogen-induced responses was investigated following single or combined cytokine-specific monoclonal antibody (MoAb) treatment of mice before immunization with OA + Asc. Immediate hypersensitivity reactions to aggregated OA and OA-specific immunoglobulin (Ig)G2a antibody production were completely restored only when both IL-4 and IL-10 were neutralized. These findings were associated with enhanced interferon (IFN)-gamma secretion by OA-stimulated lymph node (LN) cells. In addition, the Asc-specific cytokine response in anti-IL-4 plus anti-IL-10 MoAb treated mice was shifted towards a Th1 phenotype, with an increase in IFN-gamma and IL-2 levels and a decrease in IL-4, but not in IL-10, levels. Consequently, Asc-specific IgG2a antibody production increased, whereas IgE titres diminished in these animals. These results indicate that IL-4 and IL-10 act together in the Asc-induced mechanism of antigen-specific pansuppression. In contrast, modulation of Concanavalin A (Con A)-induced cytokine responses in Asc-immunized mice appears to be essentially mediated by an IL-4-dependent mechanism, since the neutralization of just IL-4 (and not of IL-10), either in vivo or in vitro, changed the cytokine profile from a Th2 towards a Th1 type. However, OA and Asc-specific cell responses were not modified by either anti-IL-4 or by anti-IL-4 + anti-IL-10 MoAbs in vitro treatments, suggesting that the induction of a Th2 response to Asc components concomitant to OA immunization has a strong suppressive effect on the priming stage of OA-specific Th1 type response.

Functional analysis of pneumolysin by use of monoclonal antibodies

We have produced a panel of monoclonal antibodies to pneumolysin, the membrane-damaging toxin from Streptococcus pneumoniae. We have used these antibodies to identify three regions of the toxin sequence that are involved in the lytic mechanism of this toxin. Two of these sites probably form the cell binding site of this toxin. Antibodies to the third site inhibit the lytic action of this toxin but not the binding of this toxin to cells. This site is engaged in the oligomerization process involved in the formation of pores in cell membranes. Two of these epitopes are also present in the related toxin perfringolysin O.