Interleukin-4 regulates the interleukin-2 receptors on human peripheral blood B lymphocytes

Conjugated linoleic acids alleviate the immunosuppression of peripheral blood T lymphocytes in broiler chickens exposed to cyclosporin A

The immunoregulatory actions of conjugated linoleic acids (CLA) of relevance immunosuppression were investigated. To test the hypothesis that CLA ameliorate immunosuppression, we developed the immunosuppressive model of peripheral blood T lymphocytes in broiler chickens induced by cyclosporin A. Peripheral blood T lymphocytes of broiler chickens were cultured with media containing various concentrations (25, 50, 100, and 200 μmol/L) of c9, t11-CLA and t10, c12-CLA to investigate the effects of CLA isomers on peripheral blood T lymphocyte proliferation, interleukin-2, the activity of phospholipase C, and protein kinase C production. Results suggested that CLA alleviated the immunosuppression of T lymphocytes in broiler chickens exposed to cyclosporin A through increasing of peripheral blood T lymphocyte proliferation and interleukin-2. The 2 CLA isomers enhanced T lymphocyte proliferation at low concentration and inhibited T lymphocyte proliferation at high concentration. In addition, the effect of c9, t11-CLA was better than that of t10, c12-CLA. At the cellular level, the effects of CLA on the alleviation of immunosuppression in T lymphocytes are mainly attributable to increasing the signaling molecules, such as phospholipase C and protein kinase C.

Interleukin-2 and systemic lupus erythematosus--fifteen years later

Systemic lupus erythematosus (SLE) is a highly heterogeneous disorder in which multiple immunologic abnormalities have been described. In this review, we thoroughly analyse the impaired T cell production of, and response to, interleukin-2 (IL-2) characteristic of patients with SLE. Since it was first reported, several articles have provided us with enlightening, but somewhat confusing, data that reveal the complexity of the subject. The IL-2 production by T cells is part of a complex network in which a discrete alteration is capable of disrupting the whole system. On the other hand, regulatory mechanisms exist that, in an attempt to compensate the primary alteration, provoke secondary defects. Evidence indicates that this defect is not intrinsic, but rather, results from multiple microenvironmental influences that act on the T cell and modify its activation state and its cytokine production. Abnormalities in co-stimulatory mechanisms and in cytokines that may be related to the IL-2 production deficiency, have been described in patients with SLE. We also consider the information derived from murine SLE models, IL-2 knockout models and reports concerning the immune dysregulation present in patients with SLE.

Anti-immunoglobulin and anti-CD40 stimulation induces CD25 expression by resting human tonsillar B lymphocytes

In this report, the effect of ligation of a number of B-cell surface molecules upon expression of CD25, the 55-kDa inducible component of the IL-2 receptor complex found on T and B lymphocytes, is reported. IL-4 is the only cytokine apparently capable of promoting CD25 expression in human high-density quiescent tonsillar B cells; neither IL-10 nor IL-13 could induce CD25 expression. Cross-linking of the antigen receptors or CD40 with antibody elicited CD25 expression in a dose-dependent manner. Stimulation with anti-CD40 promoted CD25 expression in approximately 25% of B cells, while anti-Ig caused 80% or more of cells to become CD25+. In experiments where the stimuli were used in combination, some additive effects upon CD25 expression were noted, but no obvious synergistic effects could be detected.

Exercise and the immune system. Natural killer cells, interleukins and related responses

The main methods for the evaluation of natural killer (NK, CD16+ CD56+) cells, interleukins and related subsets of lymphocytes are briefly described. Moderate endurance exercise causes either no change or an increase in lymphocyte and NK cell counts, total T cell (CD3+) count, the ratio of T helper (CD3+ CD4+) to T suppressor (CD3+ CD8+) cells, mitogen-induced lymphocyte proliferation, serum immunoglobulin levels and in vitro immunoglobulin production. Plasma levels of interleukin-1 increase but interleukin-2 (IL-2) levels generally fall. Decreases in plasma IL-2 levels reflect increased expression of beta (CD122) receptors for IL-2, and thus increased binding of IL-2, changes in cell distribution or a lesser production of IL-2 by peripheral blood mononuclear cells. Exercise to exhaustion induces adverse changes in many of these indices of immune function, particularly if the physical activity is accompanied by psychological or environmental stress. Moderate, appropriately graded training reduces the adverse reactions initially associated with a given bout of exhausting exercise, and cross-sectional comparisons show an increased expression of beta IL-2 receptors on the peripheral blood mononuclear cells of trained individuals. However, excessive training, nutrient deficiency and/or muscle damage has adverse consequences for both the production of interleukins and the response of the immune system to these cytokines.

Differential effects of interleukin-2 and interleukin-4 on immunomodulatory role of platelet-activating factor in human B cells

Platelet-activating factor (PAF), a naturally occurring phospholipid cytokine, is a potent mediator of allergic and inflammatory reactions, as well as a modulator of immune responses. In the present study we showed that PAF is involved in early B-cell activation, as demonstrated by the increased cyclic AMP (cAMP) generation by PAF in a time- and dose-dependent manner in anti-mu antibody- plus B-cell growth factor-activated normal human peripheral blood B lymphocytes. PAF also regulated differentiation by causing a biphasic response on immunoglobulin M (IgM) production with an inhibitory signal generated at 10(-6) M and a stimulatory signal generated at 10(-8) to 10(-10) M. PAF enhanced IgA secretion. The regulation exerted by PAF was shown to be specific because the addition of the PAR antagonist CV-3988 abrogated these effects and the inactive form of PAF, lyso-PAF, induced neither cAMP generation nor immunoglobulin secretion in normal human B cells. Other cytokines, interleukin-2 (IL-2) and IL-4, potent mediators of the immune response, were unable to elicit a cAMP response in B cells. However, the addition of PAF (10(-6) M) with wither IL-2 or IL-4 enhanced cAMP production above the levels enhanced by the addition of PAF alone. IL-2 or IL-4, individually, stimulated IgM production, yet costimulation with PAF resulted in a differential effect between IL-2 and IL-4. PAF down-regulated the IL-4-induced IgM secretion, whereas the IL-2-induced IgM secretion was enhanced. The presence of CV-3988 returned all valued to those obtained with IL-2 or IL-4 alone, demonstrating the specificity of PAF. These data suggest that PAF is an important B-cell immunomodulator which can interact with other leukocyte cell mediators.

Analysis of high and low responses to Staphylococcus aureus and interleukin 2 in human B lymphocytes

Fixed protein A-bearing staphylococci (SAC) stimulate human B cells via surface Ig, whereas IL-2 has been reported to provide a sufficient second signal for proliferation and differentiation. Using an ELISPOT assay to count cells secreting IgM, IgA, and IgG and flow cytometry with acridine orange to assess cell cycle progress, we have found that the purified B lymphocytes of a substantial minority (5/13) of healthy volunteers with normal serum Ig levels failed to differentiate to Ig secreting cells (ISC) in response to SAC + IL-2 (IgM, IgA, or IgG secreting cells, < 5% of input B cells). High-responders generally formed 10-35% ISC. The proportions of B cells expressing IgG, IgA, IgM, or IgD were not different in the two groups. By average linkage cluster analysis, SAC/IL-2 high- and low-responders were shown to fall into two separate populations with respect to ISC. High- and low-responders tended to remain in the same group with repeated testing over several months, although some convergence was seen. The low-responders also showed significantly less advancement to late G1 and S phase than the high-responders, in the presence of SAC +/- IL-2. Induction of IL-2 receptors on B cells by SAC + IL-2 was much greater in high-responders than in low-responders, as shown by flow cytometry with phycoerythrin-conjugated IL-2. However, SAC + IL-2 induced transferrin receptors normally in low-responders, showing that some early activation steps occur in these cells. Low-responder B cells often improved their responses in the presence of macrophages and T cell supernatants. Finally, bypassing the surface Ig pathway using anti-CD3-activated T cells to stimulate B cells produced normal differentiation in low-responder B cells. Thus a subset of clinically normal individuals possesses B cells which fail to express IL-2 receptors, proliferate, and differentiate normally in vitro in response to SAC + IL-2 yet can respond well to alternative activation pathways via T cells, monocytes, and their products.

Interleukin 10 (IL-10) upregulates functional high affinity IL-2 receptors on normal and leukemic B lymphocytes

Interleukin 10 (IL-10) has recently been shown to induce normal human B lymphocytes to proliferate and differentiate into immunoglobulin (Ig)-secreting cells. Herein, we show that IL-10 also promotes DNA synthesis and IgM production by anti-CD40 activated B cell chronic lymphocytic leukemia (B-CLL). Most strikingly, IL-2 and IL-10 were found to synergize to induce the proliferation and differentiation of B-CLL cells. This synergy between IL-2 and IL-10 was also observed with normal B cells which proliferated strongly and secreted large amounts of IgM, IgG, and IgA. The observed synergy is likely to be due to the IL-10-induced increase of high affinity IL-2 receptors on both normal and leukemic B cells. This increase of high affinity receptor is associated to an increase of Tac/CD25 expression that can be detected by flow cytometric analysis. Taken together, these results indicate that IL-10 permits anti-CD40 activated B cells to respond to IL-2 through an induction of high affinity IL-2 receptors. This effect of IL-10 may partly explain how T cells, which activate B cells in a CD40-dependent fashion, induce B cell proliferation and differentiation mostly through IL-2.

Cellular signalling mechanisms in B lymphocytes

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Interleukin 5 up-regulates high-affinity interleukin 2 receptor expression by human resting peripheral T cells: a comparison with the effect of interleukin 4 on B cells

The separate regulation mechanisms of cytokines on two classes of interleukin 2 receptors (IL-2R) on human peripheral T and B cells were analyzed by a flow cytometer using a double stain with IL-2R alpha (55 kilodalton Tac) and IL-2R beta (75 kilodalton mik beta 1, mik beta 3). Although the expression of IL-2R alpha by T cells was slightly enhanced by IL-2 and IL-4, expression of the beta chain was diminished by both cytokines. IL-5 by itself did not alter the expression of either IL-2R alpha or beta, but preculturing with IL-2 for 24 h followed by IL-5 for another 24 h induced an increase in IL-2R alpha expression and in simultaneous alpha/beta chain expression. Increased numbers of high-affinity IL-2R were confirmed by 125I binding assays. On B cells, IL-4 increased alpha, beta, and simultaneous alpha/beta chain expression, but IL-4-treated B cells did not show an increased number of high-affinity IL-2R.