A cell motility-stimulating factor has been isolated, purified, and partially characterized from the serumfree conditioned medium of human A2058 melanoma cells. We term this activity "autocrine motility factor" (AMF). AMF has the properties of a protein with an estimated size of 55 kDa. At concentrations of 10 nM or less, AMF stimulated the random or directed motility of the producer cells. However, AMF is not an attractant for neutrophils. Amino acid analysis of the purified AMF protein revealed a high content of serine, glycine, glutamic acid, and aspartic acid residues. The activity of AMF was not replaced or blocked by known growth factors such as epidermal growth factor or type p transforming growth factor.
SummaryT cell-independent type 2 (TI-2), in contrast to T-dependent, antigens stimulate the production of murine IgG3. To investigate a possible role for cytokines in mediating the induction of this IgG subclass, we established an in vitro polyclonal model system for studying TI-2 antigen-mediated B cell activation by using dextran-conjugated anti-IgD antibody (o~6-dex). We demonstrate that interferon "r (IFN-7) stimulates, and interleukin 4 inhibits, the expression of IgG3 by c~&dex-activated cells. The production of IFN-'r by non-T cells in response to bacterial products, possibly capsular polysaccharides, may provide an explanation underlying the ability of TI antigens, which are unable to directly stimulate T cell-derived cytokines to induce Ig isotype switching.ttle is known regarding the parameters that regulate the humoral immune response to T cell-independent type 2 (TI-2) I antigens. Such antigens, exemplified by the haptenated polysaccharides, are typically abundant in bacterial cell walls. Immunization of mice with this class of antigen, in contrast to T cell-dependent antigens, stimulates a significant increase in serum levels of antigen-specific IgG3 (1). Since Ig class switching is widely viewed as a process that is regulated by the release of T cell-derived cytokines, the ability of TI-2 antigens to stimulate IgG3 production is especially intriguing. In this regard, it is of interest that no cytokine has been described that regulates its synthesis in a selective and positive manner.The study of B cell responses to TI-2 antigens has been hampered by the low frequency of B cells specific for a given immunizing antigen. We recently described a model system in which resting murine mlgD + B cells are polyclonally activated in vitro in a manner similar to the specific antibody response mediated by the prototypical TI-2 antigen, TNPFicoll (2, 3). Thus, like TNP-Ficoll, multiple anti-IgD mAb molecules covalently linked to a high molecular weight dextran backbone induce resting B cells to proliferate in the absence of significant Ig production. The addition of a differentiation factor, such as IL-5, stimulates the secretion of large amounts of polyclonal Ig by dextran-conjugated anti-IgD an-1 Abbreviations used in this paper: o~-dex, dextran-conjugated anti-IgD antibody; TI-2, T cell-independent type 2.
Normal human T lymphocytes incubated with adenosine (10 pAM) for 30 min at 37C show an increase in the percentage of cells expressing receptors for the Fc portion of IgG (RFc,) and the OKT8 antigen, while the proportion ofOKT4' cells decreases. These effects occur exclusively in a subset of T cells with theophylline-resistant sheep erythrocyte receptors (TR cells (2)(3)(4)(5).Although adenosine receptors have not been characterized in human T lymphocytes, many studies suggest that the pharmacologic action ofadenosine on cells requires binding ofadenosine to specific membrane receptors (6, 7). The occupied receptors activate adenylate cyclase and it is the elevated cAMP levels that mediate the transduction ofadenosine effects. Adenosine receptors capable of activating adenylate cyclase have been termed R sites and require that the ribose ring of adenosine be unmodified. R-site adenosine receptors are located on the outer surface of the cell membrane. In contrast, a second type of adenosine receptor inhibits adenylate cyclase activity. These receptors, termed P sites, require an unmodified purine ring and are thought to be located on the inner surface of the cell membrane.Systemic lupus erythematosus (SLE) is an autoimmune disease associated with impaired suppressor T-cell function during active disease. Multiple defects in immunoregulatory mechanisms have been found in SLE by using a variety of in vitro assay systems (8, 9). In particular, although concanavalin A-treated normal T cells suppress both cellular and humoral immune responses in vitro, SLE T cells do not develop suppressor activity in response to concanavalin A (8). Similarly, SLE T-helper cells do not develop suppressor activity or show changes in the proportions of cells expressing OKT4, OKT8, and RFcl, when treated with adenosine (ref. 10; unpublished results).We have investigated both the immunologic and the pharmacologic events that occur when normal and SLE T-helper/ inducer lymphocytes are treated with adenosine. Our data suggest that some of the immunoregulatory defects observed in SLE T lymphocytes may be due to abnormalities in adenosine receptor-mediated cAMP metabolism.MATERIALS AND METHODS SLE Patients and Normal Controls. Nine individuals ranging from 19 to 40 years old, with established diagnoses of SLE, were studied. The diagnosis of active SLE was confirmed clinically and serologically at the time of study and was based on the presence of (i) four or more criteria for the classification of SLE (11) The publication costs ofthis article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.
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