Lucinda H. Elliott

Modulation of T-cell function by gliomas.

Patients with primary intracranial tumors (gliomas) exhibit a profound decrease in immunity, the mechanism of which has, until recently, remained obscure. Here Thomas Roszman, Lucinda Elliott and William Brooks reveal that T cells obtained from these patients exhibit defects in interleukin 2 secretion and in expression of the high-affinity IL-2 receptor and they discuss the role played by immunosuppressive factors produced by gliomas in inducing these defects.

Immunobiology of primary intracranial tumors. VI. Suppressor cell function and lectin-binding lymphocyte subpopulations in patients with cerebral tumors.

Peripheral blood lymphocytes obtained from patients with primary intracranial tumors were assessed for the presence of Concanavalin‐A‐activated, glass‐adherent, and spontaneous, nonspecific suppressor cells. Additionally, the effect of indomethacin on phytohemagglutinin (PHA)‐induced blastogenesis was determined. No significant differences in cellular suppressor mechanisms in these patients and normal controls were observed. However, shifts in lymphocyte populations were demonstrable when cells were separated according to quantification of PHA‐L surface binding sites by flow microfluorometry. Therefore, although impaired cellular responsiveness in patients with cerebral neoplasms does not appear to be due to alterations in suppressor‐cell function, changes in lymphocyte subpopulations occur that may be induced as an immunobiological consequence of primary central nervous system neoplasia and contribute to suppressed host immunocompetence.

Suppression of high affinity IL-2 receptors on mitogen activated lymphocytes by glioma-derived suppressor factor

SummaryPreviously we have reported that human glial tumor cells secrete a factor(s) which suppresses the mitogen responsiveness of normal human peripheral blood lymphocytes (PBL) in a dose dependent manner. In this study we extend these observations and explore the possible mechanisms by which glioma-derived suppressor factor(s) (GSF) modulates lymphocyte reactivity. Preincubation of lymphocytes with GSF for 2 hrs induces suppression of lymphocyte mitogen responsiveness. GSF also inhibits production of interleukin-2 (IL-2) by mitogen activated human T-cells. Addition of delectinated or recombinant IL-2 to mitogen activated human T-cells in the presence of GSF does not restore the normal proliferative response of these cells. These findings suggest that GSF induces a defect in the expression of the receptor for IL-2 (IL-2R) on activated T-cells. Binding studies with radiolabeled IL-2 demonstrated that GSF suppresses and in some cases completely inhibits the expression of functional high affinity IL-2R on activated T-cells, thereby, preventing association of IL-2R with its receptor and the subsequent progression of the cell into the proliferative stage of the cell cycle. These cellular defects induced by GSF closely parallel the observed defects noted in T-cells obtained from patients with gliomas, indicating that the factors elicited from glial tumors may be responsible for the immunological deficits observed in patients with primary malignant intracranial tumors.

Inhibition of anti-CD3 monoclonal antibody-induced T-cell proliferation by dexamethosone, isoproterenol, or prostaglandin E2 either alone or in combination

Summary1.The purpose of these studies was to investigate the modulation of the proliferation of human T cells obtained from peripheral blood by dexamethosone (DEX), isoproterenol (ISO), and prostaglandin E2 (PGE2). The former two substances interact with T cells via the glucocorticoid andβ-adrenergic receptors respectively. When occupied by their natural ligands, glucocorticosteroids and catecholamines, these receptors have a role in modulating T-cell function during stress. During the inflammatory response increased levels of PGE2 bind to their receptors on T cells and thus alter responsiveness. Proliferation of T cells was induced by immobilized anti-CD3 monoclonal antibody (mAb) in the presence or absence of an additional costimulatory signal delivered by anti-CD28 mAb.2.Various physiologic concentrations of DEX, ISO, or PGE2 were added at the time of initiation of the cultures and subsequent proliferation of the unstimulated T cells was determined. The results demonstrate that physiologic concentrations of all three of these agents inhibit the anti-CD3 mAb-induced proliferation of T cells.3.Although DEX and PGE2 were equipotent in suppressing T-cell proliferation, ISO was much less effective.4.Because concomitant elevations in the peripheral levels of these substances may occur, experiments were performed to determine the T-cell inhibitory effects of DEX together with either PGE2 or ISO. Synergistic suppression of T-cell proliferation was observed when various concentrations of DEX and PGE2, but not DEX and ISO, were added to cultures. This synergistic suppression could not be explained by an increase in cAMP accumulation in T cells stimulated with DEX and PGE2.5.Finally, the addition of anti-CD28 mAb to anti-CD3 mAb-stimulated T cells overcame much of the suppression of proliferation induced by PGE2 or ISO but less so than that induced by DEX.

Functional characterization of the insulin-like growth factor I receptor on Jurkat T cells

Insulin-like growth factor I (IGF-I) has been shown to be important in the maintenance, development, and proliferation of various types of leukocytes, particularly T cells. Radio-receptor binding assays demonstrate that Jurkat T cells bind 125I-IGF-I with an affinity of 1.77 nM (Kd) and express approximately 230 receptors/cell. Specificity studies show insulin also binds the IGF-I receptor with an affinity 20-fold lower than that of IGF-I. Interaction of IGF-I with its receptor on Jurkat T cells induces the phosphorylation of tyrosine kinase which is detectable by Western blotting. The 95,000 MW protein detected is equivalent to the molecular weight of the beta chain of the IGF-I receptor described in other types of cells. These studies characterize the binding of IGF-I to its receptor on Jurkat T cells, demonstrate that IGF-I binding induces tyrosine phosphorylation, and support the hypothesis that IGF-I is important in the induction of T cell activation.

[8] Preparation, characterization, and use of human and rodent lymphocytes, monocytes, and neutrophils

Publisher Summary This chapter describes some simple, concise protocols for the preparation, characterization, and use of leukocytes. The model systems used to examine the role of the nervous and endocrine systems in degenerative and inflammatory disease processes have ranged from simple in vitro proliferative assays to complex in vivo systems. Much of the progress that has been made in understanding the mechanisms of neuroimmunomodulation has come from in vitro studies using primary cultures of leukocytes. The chapter also describes methods that can be used to prepare leukocytes for in vitro studies, as well as methods for lymphocyte activation and analysis of second-messenger production. Several factors should be considered when designing a set of experiments. One of the most important is context.

Suppressor cell regulation of the spontaneously induced in vitro secondary antibody response

We have investigated the regulation of the spontaneously induced in vitro secondary antibody response of rabbit lymph node cells. A vigorous spontaneous IgG response was observed with the synthesis of high avidity antibody. Separation of lymph node cells on glass bead columns into a nonadherent and adherent fraction revealed that the nonadherent fraction yields a spontaneous antibody response which was three to four times greater than the response obtained with unfractionated control cells. The glass bead nonadherent cell response could be inhibited by the addition of either control or adherent cells. Characterization of the adherent cell population suggests that the suppressor cell is a macrophage. This suppressor cell regulates not only the magnitude of the response but the quality of antibody produced. In the absence of suppressor cells, glass bead nonadherent cell cultures give rise to larger numbers of antibody-forming cells producing low avidity antibody.

Inhibition of anti-CD3 monoclonal antibody-induced T-cell proliferation and interleukin-2 secretion by physiologic combinations of dexamethasone and prostaglandin E2

Summary1.The purpose of these studies was to characterize further previous observations from our laboratory indicating that physiologic concentrations of dexamethasone (DEX) and prostaglandin E2 (PGE2) added together result in synergistic inhibition of the proliferative response of T cells stimulated via the T-cell receptor CD3 signaling complex (TCR/CD3).2.Various physiologic concentrations of DEX and PGE2 were added to T cells stimulated with immobilized anti-CD3 monoclonal antibody (mAb) and cultured at optimal and suboptimal cell densities. The results demonstrate that the proliferative response of anti-CD3 mAb-stimulated T cells cultured at a suboptimal cell density is more suppressed than that of T cells cultured at optimal concentrations.3.The proliferative response of CD4+ T cells to immobilized anti-CD3 mAb was also determined in the presence of PGE2 and DEX. The data indicate that the CD4+ subset of T cells is more sensitive to the synergistic antiproliferative effects of DEX and PGE2 compared to whole T-cell populations.4.Various concentrations of DEX and/or PGE2 were added to T cells stimulated with anti-CD3 mAb and the secretion of interleukin-2 (IL-2) was determined. The results demonstrate that concentrations of DEX and PGE2 which individually do not significantly suppress IL-2 synthesis act together to inhibit the synthesis of IL-2 synergistically.5.The addition of an exogenous source of recombinant IL-2 (rIL-2) to T cells stimulated in the presence of DEX and PGE2 completely reversed the synergistic antiproliferative effect of these two compounds. This reversal was even more pronounced with T cells cultured at a suboptimal cell density. Additionally, PGE2 and DEX did not affect expression of the IL-2 receptor (IL-2R), as measured by upregulation of the alpha chain, on anti-CD3 mAb stimulated T cells.6.Collectively these data indicate that physiologic concentrations of PGE2 and DEX, which alone have no effect on anti-CD3 mAb-induced T-cell proliferation, act synergistically to inhibit T-cell proliferation as well as IL-2 synthesis.

Primary Malignant Brain Tumors

Although primary malignant brain tumors are rare among the general population, accounting for less than 2.4% of all cancer deaths, they are the second leading cause of cancer deaths among individuals under 34 yr of age, and rank fourth among cancer deaths for men between 35 and 55 yr of age. Glioblastoma multiforme represent 30% of all primary malignant tumors and 50% of all astrocytomas, and are the most common primary malignant tumor in middle-aged men. Despite significant advancements in therapy over the past 30 yr, the outcome for most patients who harbor these tumors remains poor, with an average mean survival of approx 62 wk after diagnosis and treatment. Several factors play a significant role in the poor prognosis for patients who harbor these tumors. One factor can be attributed to the aggressive growth characteristics and the highly invasive nature of gliomas. Although gliomas rarely metastasize outside of the brain, they often migrate along nerve tracks across the corpus callosum to seed secondary/tertiary sites in the brain, which frequently result in recurrences. Another factor involves the sequestration of gliomas away from aggressive immune attack in an immunologically privileged site. Finally, many studies suggest that glioma-derived soluble factors suppress immune-effector cells at the tumor site and systemically contribute to the broad-based immunocompromised state that has been observed in patients with gliomas. Thus, this tumor model offers an excellent opportunity to define mechanisms that are involved in immune modulation by soluble tumor-derived products. Furthermore, the model may provide insight into the mechanisms that contribute to immune privilege in the brain. This chapter reviews significant studies that have contributed to the characterization of the impaired immune status of patients with gliomas and the role of glioma-derived factors in the modulation of immune function in these patients.