SUMMARYThere is now considerable evidence suggesting that the plasma membrane of mammalian cells is compartmentalized by functional lipid raft microdomains. These structures are assemblies of specialized lipids and proteins and have been implicated in diverse biological functions. Analysis of their protein content using proteomics and other methods revealed enrichment of signalling proteins, suggesting a role for these domains in intracellular signalling. In T lymphocytes, structure/function experiments and complementary pharmacological studies have shown that raft microdomains control the localization and function of proteins which are components of signalling pathways regulated by the T-cell antigen receptor (TCR). Based on these studies, a model for TCR phosphorylation in lipid rafts is presented. However, despite substantial progress in the field, critical questions remain. For example, it is unclear if membrane rafts represent a homogeneous population and if their structure is modified upon TCR stimulation. In the future, proteomics and the parallel development of complementary analytical methods will undoubtedly contribute in further delineating the role of lipid rafts in signal transduction mechanisms.

Parasitic filarial nematodes infect more than 200 million individuals worldwide, causing debilitating inflammatory diseases such as river blindness and lymphatic filariasis. Using a murine model for river blindness in which soluble extracts of filarial nematodes were injected into the corneal stroma, we demonstrated that the predominant inflammatory response in the cornea was due to species of endosymbiotic Wolbachia bacteria. In addition, the inflammatory response induced by these bacteria was dependent on expression of functional Toll-like receptor 4 (TLR4) on host cells.

Previous studies using cell transfers and antibody receptor knockout mice have shown that B cells and antibodies are not essential components of the expulsion mechanism in Trichuris muris infections. Serum transfer experiments have given mixed results regarding the importance of antibodies in this infection model, and the role of B cells in initiating or maintaining T-cell responses has not been addressed. We used B-cell-deficient MT mice to determine if B cells play a role in anti-T. muris immune responses. In contrast to wild-type C57BL/6 mice, MT mice were susceptible to infection. Antigen-restimulated mesenteric lymph node cells from infected MT mice produced only naive levels of Th2-associated cytokines but had increased levels of gamma interferon. However, these mice appeared capable of mounting a Th2-dependent mucosal mastocytosis, though this was significantly delayed compared to that seen in wild-type mice. Resistance to T. muris was restored following reconstitution with naive C57BL/6 splenic B cells, as was in vitro Th2 cytokine production in response to parasite antigen. Treatment of MT mice with anti-interleukin-12 monoclonal antibody during the first 2 weeks of infection also restored immunity, suggesting that MT mice can be manipulated to expel worms at the time of T-cell priming. Additionally, treatment of MT mice with parasitespecific immunoglobulin G1 purified from the serum of resistant NIH mice prevented worm establishment, suggesting an important role for antibodies. Our results as a whole describe the first detailed report of a critical role for B cells in resistance to an intestinal nematode.

Objective. NF-B activation is associated with several inflammatory disorders, including rheumatoid arthritis (RA), making this family of transcription factors a good target for the development of antiinflammatory treatments. Although inhibitors of the NF-B pathway are currently available, their specificity has not been adequately determined. IB␣ is a physiologic inhibitor of NF-B and a potent repressor experimentally when expressed in a nondegradable form. We describe here a novel means for specifically regulating NF-B activity in vivo by administering a chimeric molecule comprising the super-repressor IB␣ (srIB␣) fused to the membrane-transducing domain of the human immunodeficiency virus Tat protein (TatsrIB␣).Methods. The Wistar rat carrageenan-induced pleurisy model was used to assess the effects of in vivo administration of Tat-srIB␣ on leukocyte infiltration and on cytokine and chemokine production.Results. Systemic administration of Tat-srIB␣ diminished infiltration of leukocytes into the site of inflammation. Analysis of the recruited inflammatory cells confirmed uptake of the inhibitor and reduction of the NF-B activity. These cells exhibited elevated caspase activity, suggesting that NF-B is required for the survival of leukocytes at sites of inflammation. Analysis of exudates, while showing decreases in the production of the proinflammatory cytokines tumor necrosis factor ␣ and interleukin-1␤, also revealed a significant increase in the production of the neutrophil chemoattractants cytokine-induced neutrophil chemoattractant 1 (CINC-1) and CINC-3 compared with controls. This result could reveal a previously unknown feedback mechanism in which infiltrating leukocytes may down-regulate local production of these chemokines. Conclusion. These results provide new insights into the etiology of inflammation and establish a strategy for developing novel therapeutics by regulating the signaling activity of pathways known to function in RA.NF-B is a blanket term referring to homodimers and heterodimers of a subset of the Rel family of transcription factors (1,2). Five members of the NF-B family have been identified in mammals: RelA (p65), RelB, and c-Rel, which contain transactivation domains, and p50 and p52, which are expressed as precursor proteins p105 (NF-B1) and p100 (NF-B2), respectively. The p50/p65 dimer is the most common form found in the cytoplasm of unstimulated cells, where it is usually bound to the ␣-or ␤-isoform of the inhibitor of B (IB␣ or IB␤) via ankyrin repeats (3).

The serum parasite-specific antibody responses of different mouse strains infected with Trichuris muris reflect the nature of the T-helper response mounted by the host, in that resistant Th2-responding strains, such as BALB/K, produce immunoglobulin (Ig)G1 and susceptible predominantly Th1-responding strains, such as AKR, produce IgG2a and IgG1. However, the kinetics of antibody production in the sera, as determined by enzyme-linked immunosorbent assay, do not reflect infection status in that resistant strains can expel their worm burdens before antibodies are detectable in the sera. Here, we show that parasite-specific antibody production by in vitro lipopolysaccharide-stimulated mesenteric lymph node cells (MLN) not only correlate with serum antibody isotypes, but also follow expulsion kinetics. Additionally, the antibody levels seen locally match changes in absolute B220+ cell numbers in the MLN (determined by flow cytometry) and changes in MLN parasite-specific plasma cells in the MLN (determined by ELISPOT). These results show that B cell responses are tightly regulated locally in both resistant and susceptible strains of mice infected with T. muris.