Modulation of human T cell functions by surface sulphydryl groups: differential effects on IL-2 production and responsiveness

Increased cell surface free thiols identify effector CD8+ T cells undergoing T cell receptor stimulation

Recognition of peptide Major Histocompatibility Complexes (MHC) by the T cell receptor causes rapid production of reactive oxygen intermediates (ROI) in naïve CD8⁺ T cells. Because ROI such as H₂O₂ are membrane permeable, mechanisms must exist to prevent overoxidation of surface proteins. In this study we used fluorescently labeled conjugates of maleimide to measure the level of cell surface free thiols (CSFT) during the development, activation and differentiation of CD8⁺ T cells. We found that during development CSFT were higher on CD8 SP compared to CD4 SP or CD4CD8 DP T cells. After activation CSFT became elevated prior to division but once proliferation started levels continued to rise. During acute viral infection CSFT levels were elevated on antigen-specific effector cells compared to memory cells. Additionally, the CSFT level was always higher on antigen-specific CD8⁺ T cells in lymphoid compared to nonlymphoid organs. During chronic viral infection, CSFT levels were elevated for extended periods on antigen-specific effector CD8⁺ T cells. Finally, CSFT levels on effector CD8⁺ T cells, regardless of infection, identified cells undergoing TCR stimulation. Taken together these data suggest that CD8⁺ T cells upregulate CSFT following receptor ligation and ROI production during infection to prevent overoxidation of surface proteins.

Growth and survival of B-chronic lymphocytic leukaemia cells

Although chronic lymphocytic leukaemia of B cell type (B-CLL) is the most common form of leukaemia in the Western world, several questions about the biology of B-CLL remain to be clarified. To obtain a conceptual model for B-CLL, defined as a relentless accumulation of resting B-CLL cells, it is particularly relevant to ask which cell type is the normal counterpart of B-CLL; what is the site of proliferation; which signals are involved in the recruitment and induction of proliferation and which signals contribute to the survival of the B-CLL cells? The significance of the studies on B-CLL cells in vitro for the interpretation of the in vivo situation may be questioned since they oversimplify the multiple and complex cellular interactions that occur in vivo. However, the in vitro studies have been instrumental in elucidating signals that may regulate growth, differentiation and survival of B-CLL cells. This knowledge, herein reviewed, can be used to put forward a hypothesis on B-CLL cell regulation in vivo.

Quantitation of IL-2Rp75 (CD122) expression on mononuclear cells in rheumatic disease

OBJECTIVE

To compare expression of the p75 chain of the interleukin-2 receptor (IL-2Rp75, CD122) on peripheral and synovial mononuclear cells in rheumatoid and non-rheumatoid inflammatory arthritis.

METHODS

Peripheral blood (PBMC) and synovial (SFMC) mononuclear cells were isolated from subjects with rheumatoid arthritis (n = 16) and non-rheumatoid inflammatory arthritis (n = 12). PBMC were isolated from six healthy controls. Expression of CD122 was examined using indirect immunofluorescence and quantitative flow cytometry.

RESULTS

There was no difference in IL-2Rp75 expression on PBMC from rheumatoid arthritis patients, non-rheumatoid arthritis patients, and controls. In subjects with rheumatoid arthritis there was no difference in IL-2Rp75 expression on PBMC and SFMC. However, in the non-rheumatoid arthritis group there was an increase in IL-2Rp75 expression on SFMC compared with PBMC (P = 0.0032). On SFMC there was a greater expression of IL-2Rp75 in non-rheumatoid arthritis than in rheumatoid arthritis (P = 0.0007). Expression was greater on CD8 positive cells and in subjects with shorter duration of disease.

CONCLUSIONS

The p75 chain of the IL-2 receptor, an important T cell activation antigen, is not upregulated in synovial fluid. This appears to be a disease specific defect and provides further support for the concept of "frustrated" or incomplete T cell activation in this disease.

Reactivity of an active center analog of Cu2Zn2superoxide dismutase in murine model of acute and chronic inflammation

The antiinflammatory efficacy of CuPu(Py)2 ([[N,N'-bis(2-pyridylmethylene)-1,4-butanediamine] (N,N',N'',N''')]-Cu2+), a serum stable active center analog of Cu2Zn2superoxide dismutase (SOD), was tested in vitro and in vivo in male Wistar rats suffering from potassium peroxochromate-induced inflammation. Parameters including 99mTc gamma-scintigraphic imaging, the arthritis score, the plasma superoxide dismutase activity, the inhibition of plasma sulfhydryl depletion as well as mitogenic and phagocytic responses were used to quantify the disease activity. All parameters improved impressively during the treatment with CuPu(Py)2 and resembled those of healthy animals after 21 days. The arthritis score was inhibited by 80% (P > 0.001) and the plasma SOD activity enhanced by 380% (P > 0.001). The depletion of plasma sulfhydryls and the leukocytic responses to concanavalin A, tetradecanoylphorbolacetate, and lipopolysaccharide were significantly reduced (P > 0.001) and correlated well with the arthritis score. The collapse of antioxidant defenses in human plasma as well as the depolymerization of hyaluronic acid was mimicked in vitro and successfully inhibited by CuPu(Py)2. Oxidant-induced injury of plasma components during the aqueous decay of potassium peroxochromate were demonstrated to activate the oxidative burst of phagocytes in human blood. The role of impaired pro- and antioxidant balances in the etiology of inflammatory and autoimmune rheumatic diseases is discussed.