Interleukin 1 is more than an interleukin

Human monocyte/macrophage activation and interleukin 1 generation by biomedical polymers

In vitro cell culture techniques were used to evaluate the effect of several clinically significant biomedical polymers on monocyte activation and Interleukin 1 (IL1) production. Isolated human peripheral blood monocytes were cultured in the presence of a panel of five biomedical polymers routinely used in a variety of clinical applications: Polyethylene (PE), silica-free poly-dimethylsiloxane (PDMS), woven Dacron fabric, expanded polytetrafluoroethylene (ePTFE) and the segmented polyurethane, Biomer. Monocytes generated IL1 in the presence of all five materials. Maximal levels of IL1 were generated at 24 h in monocyte-polymer cultures supplemented with serum and additionally stimulated with lipopolysaccharide (LPS). No difference was observed due to serum source. Results from cultures supplemented with fetal bovine serum were not significantly different from those obtained with human serum supplemented cultures. The thymocyte proliferative activity generated by monocytes in the presence of these biomedical polymers was neutralized by a specific polyclonal anti-IL1 antiserum. Statistically significant differences in IL1 production were observed between polymers, allowing their classification according to reactivity into high (Dacron, PE), intermediate (ePTFE) and low (Biomer, PDMS) reactive groups.

Paf-acether (platelet-activating factor) and interleukin-1-like cytokine production by lipopolysaccharide-stimulated glomeruli

The production of inflammatory mediators by glomerular cells may be instrumental in the development of pathophysiological alterations during glomerulonephritis. Since bacterial lipopolysaccharide (LPS) is a naturally occurring immunological stimulus, we studied its inflammatory effects on isolated renal glomeruli. LPS stimulation of human and rat isolated glomeruli resulted in a dose- and time-dependent platelet-activating factor (paf-acether) production. Maximal paf-acether generation (1.04 to 1.50 ng/mg protein) (n = 18) was obtained when glomeruli were stimulated for periods of 1 to 4 hr and with 1-2 micrograms/ml LPS. Paf-acether derived from human and rat glomeruli exhibited identical biological and physicochemical characteristics. In addition, rat glomeruli stimulated with doses of LPS from 100 ng to 50 micrograms/ml released an Interleukin-1 (IL-1)-like cytokine differing in part from that described in cultured mesangial cells. Maximal release of IL-1-like activity by rat glomeruli was obtained after 24 to 48 hr incubation in the presence of LPS. After gel chromatography resolution, the glomerular cytokine presented IL-1-like activity in fractions corresponding to molecular weights of 15-35 and 4-8 kDa. The latter compounds could represent metabolites similar to those described in normal urine. Thus the local release of paf-acether and IL-1-like cytokine by glomeruli in response to bacterial stimuli may represent a prominent feature of glomerular inflammation.

A sensitive, IL-2-independent, assay for IL-1

The thymocyte costimulator (LAF) assay, the standard biological test used for IL-1 titration, has a low sensitivity and lacks specificity since it can be potentiated by the IL-2 which is frequently present in IL-1-containing biological fluids. We describe here a new IL-1 titration method which takes advantage of the capacity of a thymoma line, EL4-6.1, to differentiate and express IL-2 receptors upon stimulation by IL-1 in the presence of a suboptimal dose of phorbol diester. Membrane IL-2R measurement on this indicator cell line permits the detection of 1-2 X 10(-4) ng/ml IL-1, compared to 5 X 10(-2) ng/ml in the LAF assay. In addition, rIL-2 up to 250 U/ml has no effect on IL-1 measurement by this assay, which also exhibits a 100-fold lower sensitivity to inhibitory effects of prostaglandin, compared to the LAF assay. Finally, tumor necrosis factor alpha only exerts a weak costimulation effect at very high doses. A flow cytometry technique and an ELISA are described for IL-2 receptor detection. Due to its high sensitivity and specificity, this novel assay should now permit reliable IL-1 titration in biological fluids such as IL-2-rich lymphocyte culture supernatants.

Immunomodulators

A new era is emerging in the therapy of rheumatic disease involving the use of biologically based immunomodulators. Cytokines, such as the interleukins and interferons, are proteins produced by activated lymphoid cells which can now be synthesised by genetic engineering techniques. These agents have already been used to correct "immune deficiencies" in patients with neoplastic and inflammatory disease e.g. gamma-interferon in rheumatoid arthritis (RA). Monoclonal antibodies (mca) targeted against lymphocyte cell surface receptors or against autoantibodies have been successfully applied in human lymphoid malignancies, organ transplantation and in animal models of arthritis. Potential problems in man include the development of allergic reactions to mouse proteins and of antibody resistance. Although in its infancy, immunomodulation represents an exciting approach to the treatment of rheumatic disease.

Regulation of human natural killer (NK) cell function: induction of killing of an NK-resistant renal carcinoma cell line

Natural killer (NK)-like activity against a renal carcinoma cell line, Cur, was assessed. There was no spontaneous killing of Cur cells by human peripheral blood mononuclear cells in 4-hr assays. Cur killing was observed in 18-hr assays, but the magnitude of killing was variable and always markedly less than that against K562. Cur killing was mediated by a nonadherent, nonphagocytic lymphocyte, the activity of which could be modulated both positively and negatively by monocytes or their products. Preincubation of effectors with monocyte supernatant, interleukin 1 (IL-1), alpha-interferon (alpha IFN), or interleukin 2 (IL-2) greatly increased the magnitude of Cur killing and accelerated the kinetics of lysis. The addition of prostaglandin E2 (PGE2) during in vitro activation of NK by IL-2 profoundly inhibited subsequent Cur lysis, whereas only minimal inhibition of K562 lysis was noted. However, following activation with IL-2, lysis of Cur targets was less sensitive to the inhibitory effects of PGE2. Removal of Leu 11b(+), OKM1(+), or L-leucyl-leucine methyl ester-sensitive cells markedly decreased both Cur and K562 lysis. Moreover, CD16(+) cells purified with the fluorescence-activated cell sorter were found to mediate Cur killing. Whereas Cur and K562 lysis is mediated by phenotypically similar effector cells, the present studies demonstrate that the cytotoxic functions defined by the ability to lyse these two targets differ in response to a variety of immunoregulatory stimuli.

Inhibitor of interleukin-2 synthesis and response in rheumatoid synovial fluid

We studied the effects of a factor present in rheumatoid arthritis (RA) synovial fluid (SF) on interleukin-2 (IL-2)-dependent cell proliferation and on the production of IL-2 by mitogen-stimulated peripheral blood mononuclear cells. RA SF suppressed the responsiveness of a mouse T cell line (HT-2) to IL-2, indicating that it contained an inhibitor of the IL-2 response. When RA SF was fractionated by Sephadex G-200 gel filtration, the inhibitory activity was detected mainly in fractions with a molecular weight of approximately 150,000, but was also found in a 15-19-kd fraction. Removal of IgG from the 150-kd fraction, by means of an anti-IgG affinity column, did not reduce the activity of the fraction, nor was activity found in the eluted IgG. The inhibitory fractions reduced mouse thymocyte proliferative responses to IL-1 in the presence of phytohemagglutinin, and reduced the production of IL-2 by human peripheral blood mononuclear cells, but did not inhibit IL-1-induced human foreskin fibroblast proliferation; this suggests that the factor was not an IL-1 inhibitor. The inhibitory activity of the RA SF factor was blocked by an antibody against an inhibitor of IL-2 that was purified from a culture of the human monocytic leukemia cell line, THP-1. This finding also supports the conclusion that RA SF contains an IL-2 inhibitory factor. The observed inhibition of both IL-2 synthesis and IL-2 response suggests that the target of the inhibition was the T lymphocyte.

Copper modulation of macrophage cyclooxygenase metabolite synthesis

The effect of copper on the release of cyclooxygenase metabolites from starch elicited, rat, peritoneal macrophages was investigated. Copper sulphate, in the range 10(-6)-10(-5) M, inhibited the formation of prostaglandin (PG) E2 and thromboxane (Tx) B2, the stable metabolite of TxA2, in a dose dependent manner but had no effect on the production of 6-keto-PGF1 alpha, the stable product of prostacyclin. At higher concentrations (5 x 10(-5) and 10(-4) M) the synthesis of all three metabolites of arachidonic acid (AA) was stimulated as was the release of radioactivity from macrophages prelabelled with 14C AA. Copper had no effect on the metabolism of exogenous AA however. At 10(-4) M copper also stimulated secretion of the lysosomal enzyme, beta-glucuronidase (GUR). Copper nitrate (10(-4) M), but not zinc sulphate, also stimulated eicosanoid formation and lysosomal enzyme release. Our results are consistent with the idea that copper stimulates eicosanoid formation via an effect on PL activity.

Identification of the plasma membrane receptor for interleukin-1 on mouse thymoma cells

The plasma membrane receptor for interleukin-1 (IL-1) has been characterized from mouse EL4-6.1 thymoma cells. Following binding of IL-1 to surface labeled EL4-6.1 cells, the IL-1 binding molecule was immuno-precipitated using a rabbit antiserum against the hormone. The putative IL-1 receptor is a membrane-associated glycopeptide of Mr = 82,000 containing probably two or three N-linked glycan units as indicated by its conversion into a Mr = 60,000 polypeptide upon deglycosylation with endo-beta-N-glycosidase F.

In vivo studies of articular tissue damage mediated by catabolin/interleukin 1

A partially purified porcine synovial catabolin interleukin 1 (CF) preparation was injected intra-articularly into rabbit stifle (knee) joints. Radiolabelled CF was rapidly cleared from the joint (0.4 h). Repeated injections of CF caused a marked loss of articular cartilage glycosaminoglycan (GAG) and a great increase in synovial fluid GAG. 35SO4 uptake was inhibited. Time course experiments after a single injection produced similar loss of GAG from knee cartilages, which was maximal three days after injection. The above changes were significantly less with heat inactivated preparations. Loss of articular cartilage metachromasia was found histologically, and an acute synovitis occurred together with lymphocytic foci and plasma cell infiltration.

Interleukin 2 induces proliferation of normal "resting" human T cells in the absence of other known external stimulation

Interleukin 2(IL-2) is known to stimulate the progression of activated T cells from G1 through the rest of the cell cycle. We have demonstrated that addition of purified recombinant human IL-2 (rIL-2) to fresh normal human peripheral blood mononuclear cells (PBM), which were IL-2 receptor (Tac) negative by FACS analysis, stimulated marked proliferation of the PBM. IL-2-induced proliferation was also observed with umbilical cord blood mononuclear cells. Monocyte depletion of PBM resulted in a marked reduction of rIL-2-induced proliferative response which could be restored by adding back autologous irradiated monocytes but not by interleukin 1. The T cells preincubated with rIL-2 showed a five to six times enhanced autologous mixed-lymphocyte reaction (AMLR) compared to controls. The rIL-2-induced proliferative response of PBM was inhibited in a concentration-dependent fashion by preincubation of PBM with an anti-HLA-DR framework monoclonal antibody. The proliferating cells were shown by two-color flow cytometric analysis to be primarily Leu-1+ and Leu-4+ T cells (both leu-3+ and Leu-2+ subsets); however, 6 to 19% of responding cells had surface markers for B cells or NK cells. The data demonstrate that rIL-2 can induce proliferation of "resting" human T cells. The phenomenon may be related to a monocyte-dependent AMLR which induces IL-2 receptors and IL-2 responsiveness in a subset of T cells.

Recombinant interferon-gamma stimulates the production of human tumor necrosis factor in vitro

Human peripheral blood monocytes in culture secrete tumor necrosis factor (TNF), which can be detected with a sensitive enzyme-linked immunosorbent assay system. When recombinant human interferon-gamma (rIFN-gamma) is added to cultured cells, TNF production is increased. rIFN-gamma is also able to sustain the elevated production level of TNF over a 4-day period. Recombinant interferon-alpha (rIFN-alpha) was unable to stimulate increased TNF production. Unstimulated mononuclear phagocytes and rIFN-alpha-treated cells decreased secretion of TNF over a 4-day interval. The stimulatory effect of rIFN-gamma was dose dependent and required both new RNA and protein synthesis and was independent of endotoxin in the tissue culture medium.

Macrophage stimulation with some structurally related polysaccharides

The macrophage-stimulating properties of some structurally related polysaccharides were studied in vitro. When the polysaccharides were presented to the macrophages in a sterically fixed form, i.e. as microparticles, they induced the release of interleukin 1 (IL-1) from the macrophages. Microparticulate 1.3-beta-glucan (curdlan) induced nonspecific macrophage mediated tumour cell killing while 1.4-alpha-glucan (starch), 1.6-alpha-glucan (dextran), and 1.6-alpha-mannan were without effect. The corresponding soluble polysaccharides did not stimulate the macrophages. Kinetic studies showed that although IL-1 was released immediately after stimulation, the macrophages needed a time lag of several days to develop tumour cytotoxicity. The development of cytotoxicity paralleled binding of tumour cells to the macrophages. Resident and inflammatory peritoneal macrophages showed differences in their responses to the polysaccharides. Stationary, resident peritoneal macrophages stimulated by macroparticles secreted high levels of IL-1 but expressed a low cytotoxic activity, while newly recruited inflammatory macrophages released lower levels of IL-1 but readily killed the tumour cells. The influence of cyclo-oxygenase products on the IL-1 release and macrophage cytotoxicity was also investigated. When cyclo-oxygenase was blocked with indomethacin, a significantly higher release of IL-1, and then an increased cytotoxicity, were obtained with 1.3-beta-glucan stimulated macrophages. The results suggest that microparticulate polysaccharides may be useful for studies on the induction of macrophage differentiation and also for studies on nonspecific cellular immune responses in vitro and in vivo.

Activation of the IL-1 pathway during amplification of immune responses in tumor-bearing mice

Previous work identified certain components of the immunological network that had been activated following the adoptive immunotherapy of tumor-bearing mice. The present report shows that part of the activation process involves the IL-1 pathway. Tumor-associated macrophages (TAM) from C57BL/6J mice bearing the immunogenic sarcoma, MCA/76-9, and tumor-bearers injected with cyclophosphamide (CY) or CY plus the intravenous transfer of tumor-sensitized lymphocytes showed relatively high levels of intracellular (IC) IL-1, as demonstrated in the mitogenic and comitogenic assays. Gel chromatography of IC IL-1 and extracellular (EC) IL-1 from TAM induced to secrete IL-1 by stimulation with lipopolysaccharide indicated a single peak of activity of similar molecular size. The active fractions of the EC IL-1 were found to increase in activity as they were diluted to a maximum of 1/64, beyond which IL-1 activity declined. Fractions of the IC IL-1 showed no increased activity on dilution. Filtrates (less than 10 kDa) obtained on concentration of the IC and EC IL-1 samples prior to fractionation were shown to contain an activity (3-5 kDa) that inhibited the uptake of [3H]TdR by thymocytes in the mitogenic and comitogenic assays. Membrane-bound IL-1 activity also was expressed by TAM and this coincided with the previously reported peak Ia expression by these cells. TAM were also shown to induce strong proliferative responses by allogeneic lymphocyte. Systemic amplification of antitumor responses was detected in mice bearing progressing tumors and in those that had received combination therapy as measured both by increases in free IL-1 in the peritoneal cavity and IL-1 within the peritoneal macrophages. These observations indicate that in addition to enhancement of Ia expression, the IL-1 pathway also is activated and amplified systemically in this model system of tumor progression and rejection.

Characterization of immunologic function in homosexual men with persistent, generalized lymphadenopathy and acquired immune deficiency syndrome

A syndrome of persistent, generalized lymphadenopathy (PGL), related to the acquired immune deficiency syndrome (AIDS), has been described in homosexual men. To further characterize and correlate the immunologic status of patients with PGL with those in AIDS, we studied spontaneous and pokeweed mitogen (PWM)-induced IgG synthesis by B-cells, T-cell subsets in peripheral blood (PB), natural cytotoxicity (NC), and Interleukins (IL)-1 and IL-2 production in 39 homosexual patients (21 PGL; 13 AIDS; five asymptomatic homosexual men), in whom 32 of 35 tested (91%) had antibodies to human T-lymphotropic virus-III (HTLV-III). A profound abnormality in B-cell function was found in AIDS and PGL, consisting of high spontaneous IgG production, with paradoxic suppression of IgG synthesis after PWM. IL-2 values were more often low in AIDS when compared with PGL (P less than 0.001). The PB lymphocyte count was normal in PGL and reduced in AIDS (P less than 0.001). OKT4 "helper" cells were decreased in PGL, but even lower in AIDS (P less than 0.001), while OKT8 "cytotoxic/suppressor" cells were normal in AIDS and increased in PGL (P less than 0.01). The T4:T8 ratio was reversed in both, but more abnormal in AIDS (P less than 0.001). A decrease in NC killing was observed in AIDS when compared with heterosexual controls. Thus, patients with PGL and AIDS both demonstrate a spectrum of immunologic dysfunction, involving the cellular and humoral arms of the immune system.

Serum protease inhibitors in acute viral hepatitis

Serum levels of alpha 1-antitrypsin (alpha 1-AT) and alpha 2-macroglobulin (alpha 2-M) and, as controls, alpha 1-acid glycoprotein (alpha 1-AG) and haptoglobin were evaluated by means of laser nephelometry in 17 patients with acute viral hepatitis (AVH) type A, 16 with AVH-B, 12 with AVH-NANB and 8 with fulminant hepatitis B. On admission, alpha 1-AT levels were elevated in one third of AVH-A and AVH-B cases, but subsequently declined; alpha 2-M levels were elevated in about 40% of AVH-B patients during the 2nd, 3rd and 4th week after admission. No significant correlation was found between elevated levels of protease inhibitors and aminotransferase values or drug addiction and delta coinfection. alpha 1-acid glycoprotein and haptoglobin levels were always normal or low. Protease inhibitors did not show any elevation in fulminant hepatitis, while changes were found only in a few patients with AVH-NANB. Thus, no clearcut pattern of changes in protease inhibitors has been found in association with each type of hepatitis, although alpha 1-AT and alpha 2-M elevations are mainly found in AVH-B.

Increased release of interleukin-1 from mouse peritoneal macrophages in vitro after cisplatin treatment

The supernatants collected from cis-platin (2 micrograms, 5 micrograms, 10 micrograms, treated macrophage monolayers enhance the proliferation of thymocytes by a submitogenic concentration of con A (1 microgram/ml). The supernatants collected from the untreated macrophage monolayers show a gradual ten fold increase in the interleukin-1 (IL-1) activity during 30 min to 48 h incubation at 37 degrees C. Supernatants collected from macrophage monolayers treated with 2 micrograms/ml of cis-platin show only a marginal increase in IL-1 activity as compared to untreated monolayers. However, compared to controls, 30 to 40 fold increases in IL-1 activity were measured in supernatants collected from the macrophage monolayers incubated with 5, 10 and 20 micrograms/ml cis-platin at 37 degrees C. The IL-1 activity in supernatants collected from macrophage monolayers treated with cis platin and LPS are also compared.

Cellular changes during hypertension: a quantitative study of the rat aorta

Using rats made hypertensive by aortic ligation or by the one kidney--one clip method, we searched the aorta for morphologic clues that could explain why hypertension aggravates atherosclerosis. Both atherosclerosis and hypertension are characterized by an increased migration of mononuclear cells into the aortic intima; we therefore quantitated this phenomenon and studied its time course. In the thoracic aorta of hypertensive rats intimal cells (emigrated mononuclear cells) increased up to 15 times 2 weeks after surgery and remained stationary thereafter. In both control and experimental rats, leukocyte emigration was heavier in the thoracic aorta than in the abdominal region. A two- to threefold increase in medial smooth muscle herniae into the intima (myointimal herniae) was also found at 8 weeks, indicating a smooth muscle cell dysfunction. Electron microscopic study of the intima showed that its thickening was due to blood-borne material and also to extracellular matrix synthesized by the endothelium. Heightened secretion reflects cell activation, a condition that (in the endothelium) leads also to leukocyte adhesion. These data suggest that, in renovascular hypertension, the aortic endothelium is in an activated state, possibly through a hormonal stimulus.

Identification of a common class of high affinity receptors for both types of porcine interleukin-1 on connective tissue cells

Interleukin-1 (IL-1) is the name given to the polypeptides produced by activated mononuclear phagocytes which were originally defined as lymphocyte activating factors (LAF). Administration of IL-1 in vivo causes fever and synthesis of acute phase proteins. In vitro they have been shown to cause cartilage and bone resorption, and to stimulate fibroblasts and chondrocytes to make prostaglandins and latent collagenase. IL-1 has therefore been proposed to be an important inflammatory mediator and may be involved in the destruction of cartilage and bone that is a feature of rheumatoid arthritis and other inflammatory diseases of joints. We therefore looked for IL-1 receptors on connective tissue cells which might be targets for therapeutic intervention. Here we report the iodination, to high specific activity and with retention of full biological potency, of the two types of natural porcine IL-1. These ligands have been used to demonstrate high affinity dissociation constant (approximately 10(-10) M) specific binding sites on pig chondrocytes and synovial fibroblasts, human dermal fibroblasts and murine osteoblasts (3,000-5,000 sites per cell). Most interestingly, the two different Il-1 proteins show a similar affinity for a common class of receptors.

Stimulation of resting normal human peripheral blood mononuclear cells by fetal calf sera. Activation to an interleukin-2 responsive state

Normal adult human peripheral blood mononuclear cells which are negative for interleukin-2 (IL-2) receptors as assessed by flow cytofluorometry, acquire IL-2 receptors and IL-2 responsiveness after culture in media supplemented with fetal calf sera. Thus, in the absence of any known external stimuli, fetal calf sera used to supplement culture media can induce the transformation of resting (G0) peripheral blood mononuclear cells to an activated (G1) state. The activated (G1) cells are able to progress through the rest of the cell cycle (S, G2, M) in the presence of IL-2. As a result, studies of human peripheral blood mononuclear cells in fetal calf serum-supplemented culture media should be interpreted with appropriate caution.

Tumour necrosis factor as immunomodulator and mediator of monocyte cytotoxicity induced by itself, gamma-interferon and interleukin-1

Activated monocytes or macrophages can release soluble cytotoxic molecules capable of lysing tumour cells in vitro and thus represent an important component of the host defence mechanisms against malignancy. The recent availability of pure recombinant or natural human lymphokines and monokines and their respective polyclonal or monoclonal antibodies now makes it possible to dissect the interactions of these factors in the induction and performance of the cytotoxic event by the monocytes. Our studies indicate that pretreatment of monocytes with alpha-IFN or gamma-IFN, and also interleukin (IL)-1 or tumour necrosis factor (TNF) results in enhanced monocyte cytotoxicity. Although all these substances induce the production of IL-1 by monocytes, TNF mediates the enhanced cytotoxicity induced in monocytes by gamma-IFN, IL-1 and, in an autocrine manner, by TNF itself. Neither TNF, IL-1, gamma-IFN nor alpha-IFN mediate spontaneous monocyte cytotoxicity or that induced by alpha-IFN. Our studies thus reveal new interactions between the two monokines IL-1 and TNF and provide a dual role for TNF, as immunomodulator and mediator of monocyte cytotoxicity induced by certain specific lymphokine and monokine molecules.

Mechanism of in vitro antitumor effects of interleukin 1 (IL 1)

In vitro studies suggest that purified IL 1 beta derived from normal human peripheral blood monocytes and human myelomonocytic cell line THP-1 cell supernatants was capable of modest augmentation of NK activity of purified LGL and of promoting monocyte cytotoxicity for the human melanoma A375 target cells. In addition, purified IL 1 beta also has direct cytostatic and cytocidal effects for A375 cells. A375 melanoma cells were cloned to obtain a homogeneous population of IL 1 receptor-bearing target cells. Recombinant human IL 1 alpha inhibited the proliferation of these cells within 48-72 h in a dose-dependent manner. Similar doses of recombinant IL 1 alpha exhibited inhibitory effects on the ornithine decarboxylase (ODC) activity of A375 cells by 6-24 h. Putrescine, a nontoxic product of the ODC pathway, could prevent the cytostatic effect of recombinant IL 1 alpha on these tumor target cells. This observation indicates that inhibition of the ODC pathway is causally related to the antiproliferative effect of IL 1 on these tumor cells.

The immunoregulatory role of bone marrow. IV. Role of an immunoenhancing glycoprotein derived from murine bone marrow

Bone marrow-enhancing factor (B-EF) is the spontaneous product of whole bone marrow cells cultured in serum-free medium for a short term (24-48 hr). The factor is prepared by ultrafiltration of BMC supernates to yield a preparation with a MW of greater than 10,000. Production of the factor is not dependent upon antigenic or mitogenic stimulation of BMC, but is inhibited by treatment of BMC with cycloheximide. B-EF augments the in vitro primary PFC response to SRBC, as well as in vitro secondary IgM and IgG PFC responses to SRBC. Enhancement by B-EF is antigen dependent, genetically nonrestricted, and maximal when present at the initiation of culture. B-EF cannot induce a polyclonal antibody response like the polyclonal activator LPS. B-EF is directly mitogenic for thymocytes, bone marrow, and whole spleen cells, but fails to act as a costimulator of thymocyte proliferation in the presence of Con A. B-EF cannot support the growth of the IL-2-dependent cell line CTLL-2. Since B-EF has not been purified, the supernatant may contain more than one activity. The factor is heat labile at 65 degrees C and is sensitive to enzymatic digestion with trypsin and neuraminidase; this implies that B-EF may be a glycoprotein.

Synergistic action of gamma interferon and catalase to reverse the suppressive effect of peritoneal macrophages on concanavalin A-induced lymphocyte proliferation

The suppressive effect of normal rat peritoneal exudate cells (PEC) on concanavalin A (Con-A)-induced lymphocyte proliferation was studied. Partial suppression of proliferation was obtained by adding 3% PEC and complete suppression was observed with 6% PEC. The suppressive effect was mediated by W3/25+ plastic-adherent macrophages, which constitute about 60% of normal PEC. Addition of PEC prior to, simultaneously with, or 24 h after, but not 48 h after, the stimulation of lymphocytes with Con A resulted in suppression. Suppressed cultures produced normal or slightly increased amounts of interleukin 2 (IL-2), but the expression of the IL-2 receptor on lymphocytes was decreased. Pre-exposure of PEC to gamma interferon (IFN-gamma) resulted in decreased suppression, whereas IFN-gamma added simultaneously with the lymphocytes had no effect. Catalase reversed PEC-induced suppression and significant synergistic effects were recorded when combined with IFN-gamma. Even completely suppressed cultures were effectively protected from suppression. Indomethacin and combinations of indomethacin with catalase or IFN-gamma did not result in additional protection from PEC-mediated suppression.

Biodegradable microspheres. III: some immunological properties of polyacryl starch microparticles

The antibody responses against empty polyacryl starch microparticles and the corresponding human serum albumin (HSA)-containing microparticles were followed in mice for 30 weeks. Empty polyacryl starch microparticles were nonimmunogenic as determined by a direct, enzyme-linked immunosorbent assay (ELISA). However, when the previously nonimmunogenic particle matrix was presented to the immune system together with entrapped HSA, an antibody response was detected not only against the protein antigen, but also against the microparticles matrix as detected in an inhibition ELISA. The spheres were good adjuvants for the foreign protein (HSA) and gave nearly the same response as that obtained with Freund's complete adjuvant (FCA), while the corresponding free antigen showed no or poor immunogenicity. The effects of the microparticles on lymphocytes and macrophages were also investigated. Empty microspheres were weakly stimulatory to lymphocytes. Moreover, they stimulated macrophages to release interleukin 1 in vitro.

Concurrent enhancement of monocyte immunoregulatory properties and effector functions by recombinant interferon-gamma

Interferon-gamma is a critical factor in the activation of several mononuclear phagocyte effector and immunoregulatory properties. However, it remains uncertain if IFN-gamma is capable of concurrent activation of both functions in the same cell population. Plastic adherent mononuclear cells (80-98% MN by cytochemical criteria) were cultivated in the absence or presence of recombinant interferon-gamma (rIFN-gamma, 0.1-100 U/ml) for 48 hr. MN surface DR antigen was assessed by flow cytometry (EPICS V) after staining with monoclonal antibodies OKIa1 or L243. Exposure to rIFN-gamma (100 U/ml) increased MN surface DR antigen (mean fluorescence intensity) by 80 +/- 20% (P less than 0.01) and 121 +/- 52% (P less than 0.001), respectively, compared to untreated cells. The increase in DR antigen was maximal at 100 U/ml, dependent on protein and RNA synthesis and blocked by agents that increase cAMP levels. IL-1 activity was determined in the mouse thymocyte assay; rIFN-gamma (100 U/ml) increased IL-1 activity in the supernatants of MN cultured in medium alone from 0.5 +/- 0.2 to 7.8 +/- 4.7 U/ml (P less than 0.05), and lipopolysaccharide-stimulated MN from 20.4 +/- 19.1 to 71.7 +/- 38.9 U/ml (P less than 0.05). Following rIFN-gamma exposure, MN stimulation of the AMLR was increased at 6 days (29,269 +/- 5224 vs 13,252 +/- 4938 cpm, P less than 0.01). Spontaneous cytotoxicity (SC) and antibody-dependent cell cytotoxicity (ADCC) were studied in a 51Cr release microculture assay using the human lymphoblastoid cell line CCRF-CEM as target. SC by MN increased linearly as a function of log[rIFN-gamma] for effector:target (E:T) ratios of 5:1 (r = 0.95, P less than 0.01) and 10:1 (r = 0.99, P less than 0.01). ADCC by MN increased following rIFN-gamma exposure (100 U/ml) at E:T ratios of 5:1 (22 +/- 13 to 31 +/- 4%, P less than 0.025) and 10:1 (31 +/- 4 to 38 +/- 4%, P less than 0.01). Thus, rIFN-gamma not only activates MN effector function, but has concurrent stimulatory effects on multiple MN properties critical to immunoregulation.

Interleukin 1--a possible mediator of neural fibrosis in leprosy

Neural fibrosis in leprosy, the disease caused by the obligate intracellular bacterium, Mycobacterium leprae, is closely related to the cell-mediated immune response to this microorganism. The fibrosis appears to be due to soluble mediators released by the immune effector cells. Interleukin 1, a macrophage product that stimulates fibroblast migration, proliferation and synthetic activity, possesses the requisite properties to qualify for such a mediator.

Production of pyrogen by polymorphonuclear leukocytes during the course of casein-induced peritonitis in rabbits

Rabbits with casein-induced peritonitis were febrile only during the early stage (1.5 to 12 hours) of inflammation. At that stage, peritoneal exudate cells (PEC) had preformed endogenous pyrogen (EP), while blood leukocytes and leukocytes obtained at the later stage of the inflammatory process did not. Early PEC consisted of 99% polymorphonuclear leukocytes (PMN). As early PEC and highly purified PMN (almost 100% pure) released almost identical amounts of EP, we concluded that PMN were the EP-producing cells in the early PEC. EP from PMN of rabbits was composed of three factors with similar molecular weight (8,000 to 18,000) but different pI values (pI 7.2, 5.4, and 4.5). EP in the three fractions could not be separated from thymocyte comitogenic factor (TMF) in terms of m.w. and pI values. About 60% of EP activity and 92% of TMF activity in the culture supernatant were present in the pI 7.2 fraction. The pI 7.2 factor was weaker in EP activity and stronger in TMF activity than the other acidic fractions (pI 5.4 and 4.5). After high purification, 42 ng of the pI 7.2 factor had one unit of EP activity: one unit of TMF activity was present in 126 pg of highly purified pI 7.2 factor.

Effect of human recombinant interleukin 2 on natural killing of low density Percoll fraction cells

Human recombinant IL-2 (R IL-2) was used to validate the ability of this lymphokine to increase NK cell activity. It was found that R IL-2 was able to augment the K562 lytic activity of phagocyte-depleted mononuclear cells of low density in a dose dependent manner. This phenomenon was detectable after 24 h of incubation. Low concentrations of R IL-2 were sufficient for the activation of natural killing when the incubation time was longer than 24 h. Furthermore, IL-1 exerted an additive effect on R IL-2 induced augmentation of natural killing after 24 h, but not after longer incubation periods. Lymphocyte culture derived (L) and R IL-2 had similar effects on the K562 cytolytic potential of cells contained in low density fractions. The highest cytolytic activity was observed when Leu11a+ cells were incubated with IL-2. IL-2 induced K562 cytolytic activity was also seen after incubation of low density Leu11- cells for 48 h, 72 h, or 7 days. In cultures of low density Leu11- cells incubated with IL-2 for 7 days, a proportion of cells became Leu11+. From these findings we conclude that low density Leu11- cells are pre-NK cells which acquire natural killing potential under the influence of IL-2.

Study of the biological activities of toxic shock syndrome toxin-1. I. Proliferative response and interleukin 2 production by T cells stimulated with the toxin

The mitogenic and interleukin 2 (IL 2) production-inducing effects of toxic shock syndrome toxin-1 (TSST-1) on murine lymphocytes were investigated. TSST-1, an exotoxin produced by Staphylococcus aureus recovered from patients with toxic shock syndrome (TSS), is thought to be a causative agent of the syndrome. TSST-1 was mitogenic for splenic T cells and peanut agglutinin (PNA)-negative thymocytes, but not for T cell-depleted spleen cells, PNA-positive thymocytes or IL 2-dependent CTLL 2-cells. A factor mitogenic for CTCC-2 cells with a molecular weight of 30-35 kdaltons was obtained by stimulating spleen cells with TSST-1 and it was absorbed by CTLL-2 cells, indicating that the factor is IL 2. For substantial amounts of IL 2 to be produced, 10 ng or more of TSST-1 per ml and 48 hr or more of incubation were required. Removal of T cells abrogated the IL 2 production by spleen cells. T cells obtained by the nylon wool column method alone produced IL 2 on TSST-1 stimulation in the presence of either macrophages or a macrophage lysate containing interleukin 1. However, T cells obtained by a combination of the nylon wool column method and anti-Ia antibody treatment produced IL 2 in the presence of macrophages but not of the macrophage lysate, indicating that IL 2 production by TSST-1-stimulated T cells is absolutely dependent on the presence of accessory cells.

Interactions of stem cells and T lymphocytes contribute to the physiological control of cell proliferation in rapidly renewing tissues

Control of cell proliferation, in tissues which replicate rapidly, may be exercised, at least in part, by common populations of circulating cells. Thymus-derived (T) lymphocytes possess properties which would fit them for this purpose. Among these are the functional manifestations of 'help' and 'suppression' with respect to defined physiological processes, such as immunoglobulin production; and unique traffic patterns in blood and extra-vascular tissues, including those in non-lymphoid organs such as bone marrow, skin and gut epithelium. This tropism may involve specific chemotactic agents and result in a predominance of 'suppressor' cells in target tissues. A 'steady-state' of cell proliferation could be maintained by this mechanism which is subject to humoral modulation, for instance by corticosteroids. Influx of 'helper' T lymphocytes would stimulate cell production while an excess of 'suppressors' would diminish cell renewal, as has been observed in some forms of bone marrow aplasia. Fulfillment of these roles by T cells may depend on the expression of antigens in the HLA-DR complex and it has implications for further insight into the pathogenesis of auto-immunity and neoplasia.

Possible involvement of protein kinase C in interleukin-1 production by mouse peritoneal macrophages

Both lipopolysaccharide (LPS) and phorbol-12,13-dibutyrate (PDBu), a protein kinase C-activating phorbol ester, induced interleukin-1 (IL-1) production in mouse peritoneal macrophages. Prolonged treatment of the cells with PDBu led to the down-regulation and complete disappearance of protein kinase C. In these cells, PDBu did not increase IL-1 production, but LPS still stimulated IL-1 production although the maximum level was slightly reduced. These results suggest that protein kinase C and another unknown signal pathway are involved in LPS-induced IL-1 production.

Interleukin 1 activity produced by human rheumatoid and normal dendritic cells

Dendritic cells (DC) from the synovial inflammatory tissue and peripheral blood of patients with rheumatoid arthritis and from the peripheral blood of normal blood donors were compared with the autologous monocytes for their capacity to produce and release interleukin 1 (IL-1). Synovial DC often spontaneously released higher amounts of IL-1 activity than unstimulated and lipopolysaccharide-stimulated peripheral blood DC and monocytes. The IL-1 production by both DC and monocytes increased after stimulation with bacterial lipopolysaccharide. In contrast with synovial DC the peripheral blood DC from both patients with rheumatoid arthritis and normal controls released less IL-1 activity than peripheral blood monocytes did. Inhibition with an antiserum to IL-1 revealed that IL-1 production is important for the accessory activity of the peripheral blood DC. Thus human DC from inflammatory sites and peripheral blood produce IL-1 activity.

Effect of interferon-gamma and 1 alpha,25-dihydroxyvitamin D3 on superoxide anion, prostaglandins E2, and mononuclear cell factor production by U937 cells

Both interferon-gamma (IFN-gamma) and 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3) induce changes in the human monocytic cell line U937 that may reflect cellular differentiation. The effects of recombinant IFN-gamma and 1 alpha,25(OH)2D3 on U937 cells with regard to the release of superoxide anion (O2-), prostaglandin E2 (PGE2), and mononuclear cell factor (MCF) after stimulation with phorbol myristate acetate (PMA) were examined. PMA did not induce O2- production in untreated cells. A 3-day preincubation with IFN-gamma or 1 alpha,25(OH)2D3 resulted in a 5- to 10-fold increase in PMA-stimulated production of O2- as compared to cells preincubated in medium alone. The response was related to IFN-gamma and 1 alpha,25(OH)2D3 concentrations. In contrast, the PMA-induced production of PGE2 and MCF does not require preincubation with either IFN-gamma or 1 alpha,25(OH)2D3. These results suggest that O2- production and cytokine production (i.e., PGE2 and MCF) are modulated by different signals related to maturation processes.