Characterization of the human T cell response to antigen 5 from Vespula vulgaris (Ves v 5).

BACKGROUND: The T cell reactivity to the major allergen of bee venom, phospholipase A2, has been thoroughly characterized. In contrast, only little is known about the human cellular response to major allergens from wasp venom. OBJECTIVE: To characterize the human T cell response to antigen 5 from Vespula vulgaris, Ves v 5. METHODS: Recombinant Ves v 5 was used to establish allergen-specific T cell lines (TCL) and T cell clones (TCC) from the peripheral blood of vespid-allergic and non-allergic individuals. Ves v 5-specific TCL were mapped for T cell epitopes using overlapping synthetic peptides representing the complete amino acid sequence of Ves v 5. Ves v 5-specific TCC were analysed for antigen-induced secretion of IL-4, IFN-gamma and IL-10. RESULTS: Seventeen distinct T cell epitopes were recognized by allergic individuals among which Ves v 5(181-192) was identified as a dominant T cell epitope. Partially different epitopes were observed in TCL from non-allergic subjects and the dominant epitope Ves v 5(181-192) was not prevalent in these cultures. Ves v 5-specific TCC isolated from allergic individuals did not show the typical T helper type 2 (Th2)-like cytokine profile in response to specific stimulation, i.e. high amounts of IL-4 and low IFN-gamma. TCC from non-allergic individuals showed a Th1-like cytokine pattern. CONCLUSIONS: Our findings provide evidence that the allergic T cell response to Ves v 5 is not Th2-dominated and that different immunogenic sites on this major wasp venom allergen are recognized by allergic and non-allergic individuals.

Leflunomide inhibits transendothelial migration of peripheral blood mononuclear cells.

OBJECTIVES: To test whether the active metabolite of leflunomide (LEF-M), in addition to blocking the proliferation of activated lymphocytes by inhibiting dihydro-orotate dehydrogenase (DHODH), influences the transendothelial migration (TEM) of peripheral blood mononuclear cells (PBMC). METHODS: In an in vitro model of PBMC transmigration through an endothelial cell (EC) barrier, PBMC were re-collected in three groups: cells not adherent to the EC, cells bound to, and cells which had migrated through, the EC layer. Experiments in which cells were pretreated with LEF-M (in the absence or in the presence of uridine) were compared with parallel experiments in the presence of medium alone. RESULTS: Preincubation of EC with LEF-M led to a 36 (SEM 16)% reduction in PBMC TEM (p<0.05). Likewise, preincubation of PBMC induced a reduction in their TEM of 39 (9)% (p<0.005). Incubation of both PBMC and EC with LEF-M had an additive effect (mean reduction of 48 (6)%, p<0.005). Incubation of PBMC with LEF-M also decreased monocytic CD44 expression (p<0.005) and PBMC-hyaluronan binding (p<0.05). Incubation of cells with LEF-M and uridine in addition to LEF-M reversed the inhibition of migration, suggesting that the observed effects were due to DHODH inhibition. Fluorocytometric analysis of PBMC subsets within the migrated population showed a decrease of monocytes, but not of B or T cells, after LEF-M treatment. CONCLUSIONS: LEF-M reduces monocytic adhesion molecule expression and TEM and may thus interfere with monocyte and EC activities in RA. Thus, the clinical effects of leflunomide may, at least in part, be due to blocking cell traffic into the inflamed synovia.

Alterations of dendritic cells in systemic lupus erythematosus: phenotypic and functional deficiencies.

OBJECTIVE: Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by B cell hyperactivity and defective T cell functions, including interleukin-2 production and proliferation. The defects in T cell function may result from underlying defects in antigen-presenting cell (APC) function. The present study was undertaken to investigate phenotypic and functional characteristics of peripheral blood dendritic cells (DC), as the most potent APC, in SLE patients in comparison with healthy controls. METHODS: Samples from 25 SLE patients and 15 healthy controls were studied. To identify DC, peripheral blood mononuclear cells were double stained with monoclonal antibodies against lineage marker (lin)-specific molecules CD3, CD19, CD14, and CD16, versus CD4. DC were characterized phenotypically by flow cytometry. The stimulatory capacity of DC was determined by proliferation of T cells in the mixed lymphocyte reaction (MLR), which was assessed by measurement of tritiated thymidine incorporation in studies using granulocyte-macrophage colony-stimulating factor-activated, DC-enriched APC. Correlations between DC counts and phenotype and clinical parameters in SLE patients were determined. RESULTS: Lin-, HLA-DR+, CD4+ DC were, on average, 50% less frequent in SLE patients than in controls. Moreover, among DC, the proportions of B7+ and CD40+ cells were reduced and, in particular, the CD11c+ subset was reduced by an average of 80% in SLE patients. Functional analysis of DC-enriched APC from SLE patients revealed a diminished T cell-stimulatory capacity in both the allogeneic and the antigen-specific MLR, as compared with healthy individuals. Although the frequencies of DC were weakly inversely correlated with disease activity and/or current treatment protocols, our data suggest a disease-intrinsic defect. CONCLUSION: The considerable alterations of DC and DC subsets in SLE patients may contribute to the pathogenic mechanisms involved in the disease.