Gene expression analysis of target organs might help provide new insights into the pathogenesis of autoimmune diseases. We used global gene expression profiling of minor salivary glands to identify patterns of gene expression in patients with primary Sjögren’s syndrome (pSS), a common and prototypic systemic autoimmune disease. Gene expression analysis allowed for differentiating most patients with pSS from controls. The expression of 23 genes in the IFN pathways, including two Toll-like receptors (TLR8 and TLR9), was significantly different between patients and controls. Furthermore, the increased expression of IFN-inducible genes, BAFF and IFN-induced transmembrane protein 1, was also demonstrated in ocular epithelial cells by quantitative RT-PCR. In vitro activation showed that these genes were effectively modulated by IFNs in salivary gland epithelial cells, the target cells of autoimmunity in pSS. The activation of IFN pathways led us to investigate whether plasmacytoid dendritic cells were recruited in salivary glands. These IFN-producing cells were detected by immunohistochemistry in all patients with pSS, whereas none was observed in controls. In conclusion, our results support the pathogenic interaction between the innate and adaptive immune system in pSS. The persistence of the IFN signature might be related to a vicious circle, in which the environment interacts with genetic factors to drive the stimulation of salivary TLRs.

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Interferon-gamma (IFN-gamma) exerts both enhancing and suppressing influences on collagen-induced arthritis (CIA), depending on the route and protocol of administration. To study the role of IFN-gamma on the autoimmune process of CIA, we treated DBA/1 mice with two different rat monoclonal antibodies (mAb) to murine IFN-gamma. Treatments, given twice weekly for 4 weeks, consisted of intraperitoneal injections of either mAb. In early treatments, starting from the day of immunization with type II collagen (CII), the severity of arthritis was reduced in both groups of anti-IFN-gamma-treated mice compared with control groups. Moreover, anti-CII antibody levels decreased in the sera of these mice. CIA was also down-regulated in mice treated from days 14 or 28 post immunization. In contrast, late treatments with anti-IFN-gamma mAb either induced aggravating effects, or did not affect the course of the disease. On the other hand, administration of high doses (8 x 10(4) U three times/week) of rat recombinant IFN-gamma exerted a transient increase of CIA severity. These findings suggest that IFN-gamma may play a critical role during both the induction and the course of CIA, first enhancing the immune response, and then regulating the arthritis process.

Spectrins, components of the membrane skeleton, are implicated in various cellular functions. Understanding the diversity of these functions requires better characterization of the interacting domains of spectrins, such as the SH3 domain. Yeast two-hybrid screening of a kidney cDNA library revealed that the SH3 domain of ␣II-spectrin binds specifically isoform A of low-molecular-weight phosphotyrosine phosphatase (LMW-PTP). The ␣II-spectrin SH3 domain does not interact with LMW-PTP B or C nor does LMW-PTP A interact with the ␣I-spectrin SH3 domain. The interaction of spectrin with LMW-PTP A led us to look for a tyrosinephosphorylated residue in ␣II-spectrin. Western blotting showed that ␣II-spectrin is tyrosine phosphorylated in vivo. Using mutagenesis on recombinant peptides, we identified the residue Y1176 located in the calpain cleavage site of ␣II-spectrin, near the SH3 domain, as an in vitro substrate for Src kinase and LMW-PTP A. This Y1176 residue is also an in vivo target for kinases and phosphatases in COS cells. Phosphorylation of this residue decreases spectrin sensitivity to calpain in vitro. Similarly, the presence of phosphatase inhibitors in cell culture is associated with the absence of spectrin cleavage products. This suggests that the Y1176 phosphorylation state could modulate spectrin cleavage by calpain and may play an important role during membrane skeleton remodeling.First identified at the intracellular surface of the erythrocyte plasma membrane, spectrins (Sp) are now known to be the central components of the membrane skeleton, a ubiquitous and complex spectrin-actin scaffold located under the lipid bilayer of metazoan animal cells (for review, see references 4 and 21). Numerous studies on red cells, particularly those in hereditary hemolytic anemia, have clearly established the organization of the erythrocyte skeleton and its importance in maintaining erythrocyte shape, stability, and deformability. Spectrins are giant extended flexible molecules composed of two subunits (␣I and ␤I in red cells) which intertwine to form ␣␤ heterodimers. Spectrin exists as elongated tetramers resulting from self-association of ␣␤ heterodimers. Sp tetramers constitute the filaments of the lattice, the nodes of which are crossed-linked by short actin filaments. This spectrin-based skeleton is bound to various transmembrane proteins through two connecting proteins, ankyrin and protein 4.1.In nonerythroid mammal cells, ␣ (␣I and ␣II) and ␤ (␤I to ␤V) chains are encoded by two and five genes, respectively, each of these genes producing several isoforms by alternative splicing. Despite this diversity, all Sp chains present the same structural organization mainly made up of a succession of triple-helical repeat units, 22 for ␣ chains and 17 for ␤ chains except ␤V, which has 30 repeats. These units are characteristic of spectrin family members. They are about 106 amino acids long and folded in a coiled-coil structure made up of three helices (A, B, and C). Beside these repeat units, spectrin isoforms can also con...