Interleukin 1 alpha acts as an autocrine growth factor for RPMI 1788, an Epstein-Barr virus-transformed human B cell line

The effect of covalently immobilized rhIL-1ra-ELP fusion protein on the inflammatory profile of LPS-stimulated human monocytes

The objective of this research was to investigate whether immobilized anti-inflammatory cytokines will signal changes in the inflammatory profile of cultured monocytes. A fusion protein of recombinant human IL-1 receptor antagonist and elastin-like peptide (IL-1ra-ELP) was expressed in Escherichia coli. THP-1 human monocytes were cultured on either carboxyl-terminated self-assembled monolayers (SAMs), or SAMs with either covalently immobilized or soluble IL-1ra-ELP. LPS-stimulated monocytes exposed to either soluble or immobilized IL-1ra-ELP were prevented from cell differentiation, showed attenuated expression of pro-inflammatory cytokines, and had increased production of anti-inflammatory and pro-wound healing cytokines. These results suggest that immobilized anti-inflammatory cytokines have the potential to be immunomodulatory biomaterials.

Epstein-Barr virus immunossuppression of innate immunity mediated by phagocytes

Epstein-Barr virus (EBV) is an oncogenic human herpesvirus that persistently infects approximately 90% of the world's population. Such a remarkably sustained of viral infectivity relies on EBV's ability to evade the host immune defenses. A crucial part of this anti-EBV response is mediated by cytotoxic CD8+ T lymphocytes, which maintain a life-long control over proliferating latently-infected B cells in order to prevent these from giving rise to lymphomatous diseases. On the other hand, little has been done to assess the role of phagocytes-mediated innate immunity in the pathogenesis of EBV infection. In the course of primary EBV infection, episodes of neutropenia and monocytopenia can be observed during the acute phase of infection. According to the role of those cells in the non specific and specific immunity, such a decrease in circulating phagocytes may then temporarily affect the immune defense and potentially influence the outcome of EBV infection. Recent studies have demonstrated that EBV infects both neutrophils and monocytes and modulates several of their biological functions. This review covers the current state of our knowledge relative to the role of neutrophils and monocytes in EBV pathogenesis and describes the nature of countermeasures deployed by EBV against these cells.

Serum cytokine levels in infectious mononucleosis at diagnosis and convalescence

Infection with the Epstein-Barr virus (EBV) is common worldwide. A significant number of infected individuals develop infectious mononucleosis (IM). IM is manifested in most patients as a benign disease with mild symptoms. However, serious complications may develop in a subset of patients. Because EBV-infected B lymphocytes produce various cytokines that may provide the cells with a proliferative advantage, cytokine concentrations in serum samples taken from IM patients were measured in order to identify the cytokines responsible for the clinical manifestations of the disease. The concentrations of interleukin-1beta (IL-1beta), IL-2, IL-6, IL-8, IL-10, tumor necrosis factor-alpha (TNF-alpha), and lymphotoxin (LT) were measured using an enzyme-linked immunosorbent assay (ELISA) in serum obtained from 14 IM patients during the acute phase of the disease and during convalescence, 5 patients with identical clinical manifestations who did not have IM (sick controls), and 11 healthy volunteers. It was found that the serum levels of TNF-alpha and IL-6 were significantly high in patients with acute IM compared with the serum levels in healthy individuals (P = 0.008 and P < 0.001, respectively) but returned to normal at convalescence (P = 0.009 and P = 0.005 respectively). However, whereas TNF-alpha concentrations were significantly higher (P = 0.04) in patients with acute IM than in the sick controls, no significant difference in IL-6 concentrations was found between the two groups of patients. Changes in IL-10 concentration were not statistically significant, and IL-1beta, IL-2, IL-8, and LT were detected only sporadically. The data in this study suggest that TNF-alpha may have a specific role in causing the clinical manifestations of IM. Further studies should determine the clinical significance of TNF-alpha inhibition in IM.

Relationships between B cell cytokine production in secondary lymphoid follicles and apoptosis of germinal center B lymphocytes

In vivo or in vitro activated human B lymphocytes can produce a wide spectrum of cytokines which are involved in the regulation of hematopoiesis and of the inflammatory and immune responses. Three major B cell subsets have been identified in peripheral lymphoid organs: the germinal center (GC), the mantle zone (MZ) and the marginal zone B lymphocytes. GC and MZ B cells can be isolated as CD39- surface (s)IgD- or CD39+ sIgD+ cells, respectively. Therefore, it is now possible to investigate the cytokine producing potential of purified GC and MZ B lymphocytes. In this article, the optimal conditions for the assessment of cytokine production by human B cells are first discussed; thereafter, the spectrum of B lymphocyte-derived cytokines is described together with their possible physiological meaning. Next, data concerning the cytokines released in vitro by either GC or MZ B cells are presented. Some cytokines, such as granulocyte colony stimulating factor (G-CSF) or granulocyte-macrophage CSF (GM-CSF), are produced only by GC or MZ B lymphocytes, respectively, whereas other cytokines, such as tumor necrosis factor-alpha (TNF-alpha), interleukin 6 (IL-6) or IL-10 are synthesized by both B cell subsets. Finally, the relationships between B cell-derived cytokines and apoptosis of GC B lymphocytes are discussed, and a hypothetical model of the cytokine networks in secondary lymphoid follicles is presented. It is expected that these notions will help to clarify the pathophysiology of lymphoproliferative and autoimmune diseases.

Clinical heterogeneity reflects biologic diversity in chronic lymphocytic leukemia

As the incidence of B cell chronic lymphocytic leukemia increases in an aging population, it becomes more important to re-evaluate our understanding of the disease process and current therapy. Previous treatment strategies have been, for the most part, unsuccessful in prolonging survival and thus new approaches are needed. More intense cellular and molecular research on the biologic diversity of this neoplasm will further our understanding of the causes of clinical heterogeneity and refine our ability to predict progression. New approaches, based on alterations of neoplastic cell growth by cytokines or chemotherapeutic agents, may enable clinicians to 'customize' individual treatments based on the stages of CLL B cell differentiation and our understanding of factors involved in the regulation of apoptosis and proliferation at those stages. Taken together, these efforts should ultimately yield much new information that will lead to reduced morbidity and mortality in B-CLL, the most common form of human leukemia.

Lymphotoxin acts as an autocrine growth factor for Epstein-Barr virus-transformed B cells and differentiated Burkitt lymphoma cell lines

A critical event in B cell immortalization by Epstein-Barr virus (EBV) is the establishment of an autocrine loop where cells produce a growth factor which supports their own proliferation. We investigated the potential of lymphoblastoid cell lines (LCL) and Burkitt lymphoma (BL) cell lines to produce and respond to the cytotoxins, tumor necrosis factor-alpha (TNF-alpha) and lymphotoxin (LT). Transformation in vitro of peripheral blood B cells by EBV from seven different donors resulted in spontaneous production of both LT (11,542 pg/ml +/- 7546, mean +/- SD) and, to a lesser extent, TNF-alpha (197 pg/ml +/- 174). Similarly BL cell lines derived from in vivo transformation which developed a 'LCL-like' phenotype in vitro (group III) produced more LT (1990 pg/ml +/- 1740) than the 'group I' BL cell lines (< 40 pg/ml LT) which had maintained the original BL biopsy cell phenotype in vitro. Transformation of peripheral blood B cells to generate LCL also resulted in an increase in surface p75 (p < 0.02) and to a lesser extent p55 (not significant, ns) TNF receptor (TNF-R) expression. Similar increases in surface TNF-R (p75 p < 0.02, p55 ns) were observed on the 'group III' BL cell lines compared with the 'group I' BL cell lines. Proliferation of an LCL and a 'group III' BL cell line in vitro was via an autocrine loop since inhibition of LT reduced proliferation. This proliferation could also be blocked in the presence of the antagonistic anti-p55 TNF-R antibody, H398, but not the antagonistic antibody anti-p75 TNF-R antibody UTR-1. Furthermore, proliferation could be induced with the p55 agonistic antibody, HTR-9. In contrast to these observations with p55 TNF-R antibodies, two out of six of the 'group III' BL lines (Jijoye and Oba) only expressed the p75 TNF-R and proliferation of these cells could only be blocked by the antagonistic anti-p75 TNF-R antibody UTR-1. These data suggest that LT is an autocrine growth factor for lymphoblastoid cells, and BL cell lines which display an LCL phenotype. Furthermore, although both TNF-R are increased on the surface of these cells, this autocrine growth signal is mediated principally through binding to the p55 TNF-R.

Spontaneous production of Epstein-Barr virus by B lymphoblastoid cell lines obtained from patients with Sjögren's syndrome. Possible involvement of a novel strain of Epstein-Barr virus in disease pathogenesis

OBJECTIVE

To investigate the involvement of Epstein-Barr virus (EBV) in the pathogenesis of Sjögren's syndrome (SS) and to examine whether the spontaneous production of EBV is unique to SS B cell lines.

METHODS

B cell lines were established from peripheral blood mononuclear cells (PBMC) of patients with systemic lupus erythematosus, rheumatoid arthritis, and SS. The cord blood immortalization assay, flow cytometric analysis, and polymerase chain reaction (PCR) were used to detect EBV production by B cell lines.

RESULTS

SS B cell lines produced EBV at a higher frequency, and in significantly larger amounts, than did other B cell lines. However, no correlation with the amount of EBV DNA in the genome of B cell lines was found. PCR analysis revealed that EBV with a B95-8--like U2 region was dominant in SS B cell lines.

CONCLUSION

Spontaneous, massive production of EBV by B cell lines is unique to SS, and may contribute to the polyclonal B cell activation seen in this disease.

Heterogeneity of type-II interleukin-1 receptors. Heterogeneity of B-cell interleukin-1 binding created by dimerization of type-II interleukin-1 receptors

The binding of IL-1 alpha and IL-1 beta to two human lymphoblastoid B-cell lines, Raji and RPMI 1788, was compared with binding to the murine T-cell line, EL4. Dramatic differences in IL-1 binding were observed. Both human B-cell lines bound much less IL-1 alpha than IL-1 beta, expressed 5-10 times more receptors per cell for IL-1 beta than did the EL4 cell line, and demonstrated a large difference in the ability of IL-1 alpha to compete with IL-1 beta for binding. The B-cell lines demonstrated a low number of high-affinity IL-1 alpha receptors and a large number of IL-1 alpha receptors with a much lower affinity. Inhibition studies demonstrated that only IL-1 beta could compete for the binding of radiolabeled IL-1 beta to the B-cell IL-1R. Furthermore, SDS-PAGE analyses of lysates of the B-cell lines that had been affinity cross-linked with 125I-IL-1 alpha revealed two bands corresponding to IL-1R structures of 60 and 110 kD. These results coupled with a nonequilibrium binding study suggested a dimerization of a common type-II IL-1R polypeptide, the dimer being responsible for the high-affinity IL-1 alpha-binding site of the B-cell lines.

Effects of IL-4, IL-5, and IL-6 on growth and immunoglobulin production of Epstein-Barr virus-infected human B cells

In the present study we investigated whether interleukin-4 (IL-4), IL-5, and IL-6 could enhance the efficiency of Epstein-Barr virus (EBV) transformation for the generation of specific human monoclonal antibody (HuMAb)-producing B-cell lines directed against erythrocyte Rhesus(D) antigen. In newly EBV-infected B cells, IL-4 and IL-6 caused a comparable enhancement of proliferation and of total IgG and IgA production. IL-6 showed a much stronger effect than IL-4 on IgM production, whereas IL-4 was unique in inducing IgE production. No stimulatory effects of IL-5 on either growth or Ig production were observed. Although addition of IL-6 resulted during the early phase after EBV infection in high numbers of Ag-specific antibody-producing wells, this did not result in an increased number of stable HuMAb-secreting cell lines. When the effects of cytokines were tested on established polyclonal EBV B cells, in a high cell density culture system, only IL-6 was able to enhance Ig secretion, while no effect could be demonstrated on proliferation. These studies substantiate that IL-6 is an important regulator of proliferation and Ig production, and that it acts at distinct stages after EBV infection, but does not increase the final overall recovery of Ag-specific EBV B-cell lines.

Immunoregulatory functions of paf-acether. VI. Dual effect on human B cell proliferation

The role of paf-acether (paf), a phospholipid cytokine, in the modulation of human B cell function was investigated. Paf, from 1 x 10(-5) M to 10(-6) M, decreased B cell proliferation induced by both phorbol myristate acetate (PMA) and anti-IgM antibodies (anti-IgM Ab). By contrast, 1 x 10(-7) M to 1 x 10(-9) M paf enhanced PMA triggered, but not anti-IgM triggered B cell proliferation. B cell proliferation was modulated between 24 and 72 hr of culture indicating that the effect of paf did not merely reflect a shift in proliferation kinetics. Interestingly, paf also enhanced the spontaneous proliferation of a Burkitt lymphoma-derived B cell line, Raji, which suggests that paf can directly act on B cells. The modulatory effect of paf on peripheral blood B cells was independent of PMA concentration, yet the effect on Raji cells was dependent upon cell density. The data suggest that paf is a potent modulator of B cell function, and may be involved in the control of humoral immune response.

Development of a simple, sensitive and specific bioassay for interleukin-1 based on the proliferation of RPMI 1788 cells. Comparison with other bioassays for IL-1

The IL-1-dependent proliferation of RPMI 1788, a human EBV-transformed cell line, was used to develop a biological assay system for IL-1. Preparations of rhIL-1 alpha and rhIL-1 beta, as well as rmIL-1 beta exhibited a specific biological activity (50% of the maximal response) between 5.8 x 10(8) and 8.6 x 10(8) U/mg. Remarkably, a 3-5-fold reduced specific biological activity was noticed for rm-IL-1 alpha, viz. 1.7 x 10(8) U/mg. The IL-1-dependent proliferation of RPMI 1788 cells was compared with other IL-1 test systems, such as the IL-1-mediated induction of IL-2 in EL4-NOB-1, LBRM-33-1A5 and thymocytes, and the IL-1-driven induction of cytotoxic activity by PC60 cells, the so-called CIA assay. The cytokine-dependent growth of RPMI 1788 cells is highly specific for IL-1, and no other cytokine tested induced a proliferative response. The presence of high concentrations of rmTNF, rhTNF or rhIL-6 did not interfere with the quantification of IL-1. Additionally, we evaluated the detection of IL-1 in the presence of mitogens, phorbol ester or calcium ionophore, as well as the determination of IL-1 in serum and PF samples of human and murine origin.

IL-4 acts synergistically on the IL-2 response of an autoreactive T-cell clone; synergism correlates with increased intracellular IL-2, but not with a modified IL-2 receptor expression

TE44, an H-2b-restricted, self-reactive T-cell line, did not produce autocrine-acting growth factors, neither after antigenic nor after mitogenic activation; they remained for their proliferation completely dependent on exogenously added IL-2. Administration of IL-4, which poorly promotes growth by itself, resulted in a 5- to 10-fold enhancement of the specific biological activity of IL-2 on antigen-activated TE44-cells. This synergism was exerted nonreciprocally and required the presence of both lymphokines. IL-4 did not affect the number, nor the affinity, nor the rate of internalization of the high-affinity receptors for IL-2. However, increased levels of intracellular IL-2 were observed, suggesting an effect of IL-4 on the turnover of IL-2. This might allow a prolonged activity of IL-2 or IL-2-associated molecules inside the cell. Furthermore, the lack of autocrine growth factor production by antigen-stimulated TE44 is discussed in terms of its relationship to the autoimmune specificity of these T-cells.

Direct activation of human B lymphocytes by Candida albicans-derived mannan antigen

We have studied the activation of human resting B cells by a carbohydrate antigen, mannan, with a polymannose branched repetitive structure. Mannan has been extracted from the cell wall of the Candida albicans yeast. For this purpose, dense G0 B lymphocytes were purified from tonsils. Mannan antigen was shown to trigger B cell activation, since an increase of cell volume and RNA synthesis occurred. B cell proliferation was observed following addition of recombinant interleukin 2, but not following addition of recombinant interleukin 4 or low-molecular-weight BCGF. The B cell activation appears to be mannan-specific since B cells obtained from mannan-sensitized subjects but not from unsensitized subjects were responsive. The observation that mannan antigen can directly activate specific dense B lymphocytes can be related to the previous observation that the in vitro anti-mannan antibody production does not require a cognate T-B cell interaction.