We demonstrate that interleukin‐10 (IL‐10) can inhibit T‐cell apoptosis. T cells, within a PBMC (peripheral blood mononuclear cell) population, were stimulated via the T‐cell receptor and grown in the presence of IL‐2. These cells had less apoptosis when in the continuous presence of IL‐10, compared with cells grown in the absence of IL–10. Conversely, when stimulated and grown in the presence of neutralizing antibody to IL‐10, there was an increase in T‐cell apoptosis. The in vitro rescue from apoptotic cell death of other lymphoid cells, such as germinal centre B cells, has been shown by others to involve a Bcl‐2 pathway. We therefore investigated whether IL‐10 might affect the Bcl‐2 expression on cultured T cells. By Western blotting we demonstrated that continuous exposure of IL‐10 to T cells (within a PBMC population) enhanced the expression of Bcl‐2. Furthermore, T cells protected from apoptotic cell death by IL‐10 were indistinguishable from viable untreated cells in their ability to proliferate to either immobilized anti‐CD3 or IL‐2. Thus, we have shown that continuous culture of T cells in the presence of IL‐10 will inhibit T‐cell apoptosis because of, at least in part, the upregulation of Bcl‐2, and this is associated with a normal proliferative function.

Objective. To characterize the cytokine profile of the activated T cell population derived from the synovial membrane of rheumatoid arthritis (RA) patients. Methods. Interleukin‐2 (IL‐2) was used to select for in vivo–activated T cells from the synovial membrane of 2 patients with RA, and the cells were cloned nonspecifically. The cytokine production profile of these clones was compared with that of clones derived from peripheral blood monocytes (PBM) by stimulating all clones for 24 hours with immobilized anti‐CD3 (coated at 10 μg/ml) or phorbol‐12‐myristate‐13‐acetate (10 ng/ml) plus soluble anti‐CD3 (1 μg/ml). Interferon‐γ (IFNγ), IL‐4, and IL‐10, the cytokines that discriminate between Th1 and Th2 cells and are involved in immunoregulation, were assayed by enzyme‐linked immunosorbent assay. Results. There was a difference in the cytokines produced by the clones derived from the rheumatoid membranes compared with clones derived from the periphery. Clones derived from both membranes and PBM were mostly IFNγ‐producers, i.e., either a Th0 or a Th1 profile. There was a high proportion of IFNγ/high IL‐10‐producing cells derived from the joint, but not from the periphery. Of clones derived from the synovial membrane of each of 2 RA patients, 100% and 50% produced both 1–10 ng/ml IFNγ and >7 ng/ml IL‐10, compared with <7% of clones derived from normal or RA peripheral blood. In addition, when autologous membrane and PBM were compared, the mean concentration of IL‐10 produced by the clones derived from the synovial membrane sample was significantly different from those produced by clones derived from peripheral blood (P < 0.02). Conclusion. The cytokine profile of the T cell clones that were obtained from the RA joint after expansion with IL‐2 is distinct from that of the T cells that are predominant in PBM. This supports the concept that the T cell subsets that accumulate in the joint are not a random sample. The high level of IL‐10 production by clones derived from the synovium suggests that this cytokine may be a major contributor to the endogenous immunosuppression that occurs in RA.

This retrospective study describes 35 dogs with non-resectable, grade I-III mast cell tumours on the head or limb treated with prednisolone (40 mg m(-2) daily) for 10-14 days prior to radiotherapy (4 x 800 cGy fractions at 7-day intervals) from a 4 MV linear accelerator. Prednisolone was continued at a reduced dose rate (20 mg m(-2)) during radiotherapy and for 2 months or longer afterwards. Eighteen of 24 tumours (75%) decreased in size in response to prednisolone treatment. By 6-8 weeks following radiotherapy, 12 dogs had achieved a complete remission and 19 a partial response. Two tumours remained static and two progressed during the course of treatment. The overall response rate was 88.5%. With long-term follow-up, 11 dogs experienced local recurrence (n = 4), metastasis (n = 5) or both (n = 2). The median progression-free interval was 1031 days (95% CI 277.44-1784.56, Kaplan-Meier), with 1- and 2-year progression-free rates of 60 and 52%, respectively. Tumour grade did not predict the prognosis for this group of dogs, but tumour location did affect the outcome. Dogs with tumours located on the limb survived longer than those with tumours on the head. The combination of prednisolone with radiotherapy appears to have a useful role in the management of measurable mast cell tumours sited on the head and distal extremities.

Human CD4+ T cells have, like their murine counterparts, been classified on the basis of their cytokine profile. Th1 cells produce IL-2 and IFN-gamma, but little or no IL-4. Th2 cells produce IL-4 but not IFN-gamma or IL-2, and Th0 produce IL-2, IL-4 and IFN-gamma. As IL-2 is the most potent T cell growth factor and IFN-gamma is the strongest activator of macrophages it is not surprising that CD4+ Th1 cells are considered to be pro-inflammatory. However, unlike results in the mouse, where IL-10 is only produced by Th2 cells, human IL-10 is produced by Th0, Th1 and Th2 cells. Hence some human Th1 cells are capable of producing both pro-inflammatory (IL-2, IFN-gamma) and anti-inflammatory (IL-10) cytokines, therefore the function of these cells may not be accurately encapsulated by the 'Th1' terminology. We thus investigated the correlation of cytokine production and function in human CD4+ Th1 clones. Cytokine production (IL-2, IFN-gamma, IL-10) was measured in supernatants by ELISA after stimulation with solid-phase anti-CD3. The capacity of these supernatants to activate or inhibit T cell proliferation or LPS induced TNF-alpha production by monocytes was assessed. The ratio of IL-2/IL-10 or IFN-gamma/IL-10 was of critical importance in determining the function of the supernatants. The inhibitory effects were verified to be due to IL-10, as they were neutralized by anti-IL-10 mAb.(ABSTRACT TRUNCATED AT 250 WORDS)

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To delineate accurately the IgG subclass distribution of thyroid auto-antibodies, sera from nine patients with Hashimoto's thyroiditis were fractionated into IgG subclasses by complete depletion of the other IgG subclasses on affinity columns. All IgG subclass fractions contained thyroglobulin and microsomal (or thyroid peroxidase) antibody activity, although when compared to the total serum concentrations of IgG subclasses, IgG4 antibodies were overrepresented. However, in contrast to recent studies, this particular subclass never predominated--IgG4 antibody levels being exceeded by those of the IgG1 and IgG2 subclasses; it seems likely that these differences relate to varying sensitivity for different subclasses in previously used assay methods. This pattern of subclass activity differed from that of tetanus toxoid antibodies, which were found in six subjects. There was no light chain restriction within any subclass, showing that the overproduction of IgG4 thyroid antibodies is not of monoclonal origin. The functional affinity of subclasses for both thyroid antigens varied between patients, but IgG2 subclass fractions showed the highest functional affinity in the majority of samples. We also found that IgG2 subclass thyroid antibodies were ineffective in eliciting antibody-dependent cell-mediated cytotoxicity, as distinct from the other three subclasses. Our results show that thyroid antibodies are less restricted in their IgG subclass distribution and patients are less heterogeneous than previously described. Moreover, IgG2 thyroid antibodies are quantitatively important and differ in relative functional affinity and effector function from IgG1 and IgG4 thyroid antibodies.

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