Immune interferon. I. Production by lymphokine-activated murine macrophages

Changing the paradigm of IFN-γ at the interface between innate and adaptive immunity: Macrophage-derived IFN-γ

IFN-γ plays a critical role in the immune response to bacterial infections. It is established that IFN-γ is mainly produced by NK/ILC1 cells and T cells, and most of papers have rejected the biologic reality of alternative sources for more than 20 years. Here, we are proposing to revisit this dogma and discuss the role of macrophage-derived IFN-γ in bacterial infections. Our hypothesis is based on a panel of publications and is recently revived by our results on placenta, a chimeric organ in which the immune response is tailored to protect the fetus from mother's immune response. The culture of purified placental macrophages is associated with a production of IFN-γ that may contribute to fetal protection from bacterial infections before eliciting a Th1-like immune response potentially pathogenic for pregnancy. Hence, macrophage IFN-γ may be a novel actor of early crosstalk between innate and adaptive immunity in the context of host defense against bacterial infections.

Interferon-Gamma-Mediated Osteoimmunology

Osteoimmunology is the interdiscipline that focuses on the relationship between the skeletal and immune systems. They are interconnected by shared signal pathways and cytokines. Interferon-gamma (IFN-γ) plays important roles in immune responses and bone metabolism. IFN-γ enhances macrophage activation and antigen presentation. It regulates antiviral and antibacterial immunity as well as signal transduction. IFN-γ can promote osteoblast differentiation and inhibit bone marrow adipocyte formation. IFN-γ plays dual role in osteoclasts depending on its stage. Furthermore, IFN-γ is an important pathogenetic factor in some immune-mediated bone diseases including rheumatoid arthritis, postmenopausal osteoporosis, and acquired immunodeficiency syndrome. This review will discuss the contradictory findings of IFN-γ in osteoimmunology and its clinical application potential.

Antivirals against animal viruses

Antivirals are compounds used since the 1960s that can interfere with viral development. Some of these antivirals can be isolated from a variety of sources, such as animals, plants, bacteria or fungi, while others must be obtained by chemical synthesis, either designed or random. Antivirals display a variety of mechanisms of action, and while some of them enhance the animal immune system, others block a specific enzyme or a particular step in the viral replication cycle. As viruses are mandatory intracellular parasites that use the host's cellular machinery to survive and multiply, it is essential that antivirals do not harm the host. In addition, viruses are continually developing new antiviral resistant strains, due to their high mutation rate, which makes it mandatory to continually search for, or develop, new antiviral compounds. This review describes natural and synthetic antivirals in chronological order, with an emphasis on natural compounds, even when their mechanisms of action are not completely understood, that could serve as the basis for future development of novel and/or complementary antiviral treatments.

Production of interferon-gamma by myeloid cells--fact or fancy?

Myeloid cells are usually viewed as targets rather than producers of interferon (IFN)-gamma. However, since 1993 several studies have suggested that macrophages and dendritic cells can also secrete IFN-gamma in response to various stimuli, which led to the idea of autocrine myeloid-cell activation in innate immunity. Here, we review this concept in the light of recent findings that illustrate the necessity of specific cell markers, cell purity, sensitive single-cell cytokine detection methods, and of further insights into the developmental origin of myeloid and lymphoid cell lineages. We also discuss the possible function of intracellular IFN-gamma in macrophages and the evidence for a protective role of myeloid IFN-gamma in vivo.

IFN-gamma production by antigen-presenting cells: mechanisms emerge

The suggestion that antigen-presenting cells (APCs) produce interferon gamma (IFN-gamma) is controversial because it conflicts with the initial paradigm in which the production of IFN-gamma was restricted to lymphoid cells. However, some answers to this skepticism have been provided by recent findings of high-level production and intracellular expression of IFN-gamma by interleukin-12 (IL-12)-stimulated macrophages and dendritic cells. New data are now emerging to explain the mechanism of production of IFN-gamma vby APCs. As in lymphoid cells, IL-12-induced IFN-gamma production in APCs requires signal transducer and activator of transcription 4 (STAT4), although the precise molecular events that govern the transcription of the gene encoding IFN-gamma are enigmatic still. Understanding these processes in lymphoid, and now nonlymphoid, cells remains an important challenge.

Cytokine regulation of cellular proliferation in endometriosis

OBJECTIVE

This study was designed (1) to characterize the resident leukocyte population in ectopic endometrium (EE), (2) to assess proliferative activity of cellular components in EE, (3) to assess whether resident leukocytes in EE express IFN gamma mRNA and (4) to demonstrate endometrial epithelial cell IFN gamma receptors in EE.

STUDY DESIGN

Biopsies of EE and normal eutopic endometrium (UE) were studied immunocytochemically using monoclonal antibodies specific for CD45 leukocyte common antigen, CD3 (a T cell marker), CD11c (a macrophage marker), and Ki67 (proliferation marker). Leukocyte types were identified immunocytochemically, followed by in situ hybridization to assess expression of IFN gamma mRNA. IFN gamma receptor expression was assessed by immunocytochemistry.

RESULTS

The percentage of scattered stromal cells staining for each CD marker was greater in EE than in UE. The proliferative activity of endometrial stromal cells and epithelial cells was significantly less in EE than in UE. The overall concentration of T cells and macrophages expressing IFN gamma mRNA was significantly greater in EE than in UE. The percentage of each leukocyte type expressing IFN gamma mRNA was also greater in EE than in UE, and IFN gamma receptors were present in glandular epithelium of EE.

CONCLUSIONS

These findings support a possible paracrine role for resident leukocytes and IFN gamma in regulating cell proliferation in endometriosis.

Interferon gamma upregulates its own gene expression in mouse peritoneal macrophages

Interferon gamma (IFN-gamma) exerts a variety of immunoregulatory effects on several cell targets. It is generally assumed that IFN-gamma is specifically produced by T and large granular lymphocytes. In this study, we show that IFN-gamma is constitutively expressed in resting mouse peritoneal macrophages (PM). Treatment of PM with cycloheximide results in a significant accumulation of IFN-gamma mRNA, suggesting that a short-lived IFN-gamma mRNA accumulates when protein synthesis is inhibited. Moreover, treatment of PM with IFN-gamma also results in a clear-cut accumulation of this mRNA. This effect is not observed in murine lymphocytes from mesenteric lymph nodes (which instead produce IFN-gamma after phytohemagglutinin treatment) and in mouse cell lines. The treatment of PM with IFN-gamma also results in secretion of IFN-gamma after 24-48 h. The upregulation of IFN-gamma expression is also found in PM from anti-asialo GM1-treated nude mice. We suggest that the ability of PM to produce this IFN-gamma is indicative of an autocrine mechanism. The macrophage IFN-gamma may play a role in the regulation of cell differentiation and immune response.

Seed extract of Aeginetia indica L induces cytokine production and lymphocyte proliferation in vitro

We previously reported that the extract of seeds from Aeginetia Indica L (AIL), a parasitic plant, induces potent antitumor immunity in tumor-bearing mice and that CD4+ T cells appear to be the main contributors in the induction of antitumor resistance. The present study was set up to investigate the in vitro effects of AIL on various lymphoid cells. Spleen cells from mice pretreated with AIL every 2 days for 1 week produced interleukin 2 (IL-2), interferon gamma (IFN gamma), tumor necrosis factor (TNF) and interleukin 6 (IL-6) when these cells were stimulated in vitro by AIL. Further, we found that CD4+ T cells were main producers of IL-2 and TNF upon the stimulation with ALL in vitro, while both CD4+ and CD8+ T cells secreted IFN. On the other hand, ALL was mitogenic in vitro to T enriched splenic lymphocytes as well as B enriched splenic lymphocytes. Moreover, AIL also proliferated thymocytes and this activity was potently synergistic with a suboptimal dose of concanavalin A (Con A). Lipopolysaccharide (LPS) contamination in AIL preparation was negligible since proliferative activity of AIL to B enriched splenic lymphocytes was not influenced in the presence of an endotoxin antagonist, polymyxin B sulfate (PMB). Further, B cell mitogenic activity of AIL seems to be mediated by different mechanism(s) from that of LPS since ALL could proliferate B enriched lymphocytes of C3H/HeJ mice which do not respond to the stimulation with LPS. A well known biological response modifier (BRM), Krestin (PSK), had no ability in inducing either T or B lymphocyte activation in vitro as shown by AIL.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced expression of resident leukocyte interferon gamma mRNA in endometriosis

PROBLEM

Previous studies have shown that the endometrial epithelial/stromal cell proliferative activity of endometriosis is significantly less than that of normal endometrium and that the concentration of resident stromal leukocytes is significantly greater in ectopic than in eutopic endometrium. Other work has shown that interferon gamma (IFN gamma), secreted by resident leukocytes, inhibits endometrial cell proliferation in vitro. Accordingly, we hypothesized that the lower proliferative activity of endometriosis may be related to enhanced resident leukocyte IFN gamma production. This study was designed to assess whether resident leukocytes in endometriosis express IFN gamma mRNA and to compare this expression to that of normal endometrium.

METHODS

Biopsies of ectopic endometrium (N = 16) from women in the follicular phase and normal proliferative (N = 9) and secretory (N = 8) endometria were examined for IFN gamma expression. Using monoclonal antibodies specific for CD45 (leukocyte common antigen), CD3 (a T-cell marker) and CD11c (a macrophage marker), leukocyte types were identified immunocytochemically, followed by in situ hybridization to examine expression of IFN gamma mRNA.

RESULTS

Results demonstrated that (1) the overall concentration of T cells and macrophages expressing IFN gamma mRNA is significantly greater in endometriosis as compared to eutopic endometrium, and (2) the percent of each leukocyte type expressing IFN gamma mRNA is greater in endometriosis than in normal endometrium.

CONCLUSIONS

These findings support a possible paracrine role for resident leukocytes in regulating cell proliferation in endometriosis.

Staphylococcal enterotoxin A induced interferon (IFN)-gamma production in spleen cells from BCG-immunized mice: the IFN production is dependent on leukotriene C4 but not dependent on interleukin 2

In our previous paper, we showed that IFN was induced in sera by injection of staphylococcal enterotoxin A (SEA) in Bacillus Calmette-Guérin (BCG) immunized C57BL/6 (B6) mice. In analyzing the phenomenon in vitro, we showed that SEA induced IFN-gamma in the supernatant of the spleen cell culture from BCG immunized B6 mice and that leukotriene C4 (LTC4) from BCG activated macrophages in the spleen was involved in the IFN production from Ly 1+ T cells. On the other hand, interleukin-2 (IL-2) has reported to play an important role in the regulation of synthesis of IFN-gamma by T cells. In the present study, we examined whether IL-2 is involved in SEA-induced IFN production. The result showed that the SEA-induced IFN-gamma production was observed in spite of suppression of SEA-induced IL-2 production in spleen cells from BCG-immunized B6 mice. On the contrary, the depressed IFN production was observed in spite of high SEA-induced IL-2 production in spleen cells from their control mice. On the other hand, LTC4 production was 8 times higher in spleen cells from BCG-immunized B6 mice, high producer of SEA-induced IFN, than in that from BCG-immunized C3H mice, the low producer. We also observed that the IFN and the LTC4 production of spleen cells from BCG-immunized B6 mice was suppressed in the presence of caffeic acid and nordihydroguaiaretic acid, non-specific lipoxygenase inhibitors, and that LTC4 augmented the IFN production of normal B6 mouse spleen cells in the presence of 2-mercaptoethanol. Therefore, involvement of LTC4 rather than of IL-2 was supported in our experimental system.

Development of optimal conditions for lymphokine production by chicken lymphocytes

Chicken thymus, spleen, and bursa lymphocytes were isolated by different methods and incubated under differing conditions in order to obtain and characterize avian lymphokines. The biological activity of lymphokine-containing cell culture supernatants was measured by their antiviral activity (interferon(IFN)-units) and by their capacity to induce cytostatic effects in bone-marrow-derived macrophages (50% cytostasis-inducing dose, CID). Lymphokine production by thymus lymphocytes required concanavalin A (ConA)-stimulation, while spleen cells, when cultured at high density, released CID and IFN activities into the culture medium even without mitogen-stimulation. By way of comparison, the highest lymphokine content was found in the supernatant of lymphocyte cultures, which were incubated for 72 hours at 41 degrees C after stimulation with an optimal ConA dose. For stimulation of thymus lymphocytes 30 micrograms ConA/ml were found to be optimal, independent of serum content and cell density in the cultures. In contrast, the optimal ConA dose for spleen lymphocytes not only depended on the serum content but also on the cell density in the cultures and varied within a range of 2.5 micrograms and 45 micrograms ConA/ml.

Depression of protective mechanism during the early phase of a viral infection in tumor-bearing mice and prevention by PSK

Effector mechanisms responsible for resistance against ectromelia virus including antiviral activity of non-immune macrophages, antiviral antibody, delayed footpad reaction to viral antigen, and interferon induction after viral infection were depressed in BALB/c mice bearing syngeneic Meth A tumor. The degree of viral growth correlated well with the depression of delayed footpad reaction, antibody production, and interferon induction. Therefore, modification of macrophage functions by a tumor-bearing state and treatment with PSK may contribute to this modification of antiviral resistance, at an early phase of infection. Cytotoxic activity may not be the principal effector, since the cytotoxicity was induced in normal and tumor-bearing mice to almost the same extent yet an extensive viral growth occurred only in the latter.

Gamma interferon is spontaneously released by alveolar macrophages and lung T lymphocytes in patients with pulmonary sarcoidosis

Gamma interferon (IFN gamma) is a potent immune mediator that plays a central role in enhancing cellular immune processes. This study demonstrates that while lung mononuclear cells from normal individuals spontaneously release little or no interferon (less than 10 U/10(6) cells per 24 h), those from patients with pulmonary sarcoidosis spontaneously release considerable amounts (65 +/- 20 U/10(6) cells per 24 h, P less than 0.02 compared to normals). Furthermore, cells from patients with active disease release far more interferon than those from patients with inactive disease (101 +/- 36 compared to 24 +/- 8 U/10(6) cells per 24 h, P less than 0.02). Characterization of this interferon using acid sensitivity, specific antibody inhibition, and target cell specificity criteria demonstrated that it was almost entirely IFN gamma. This spontaneous release of IFN gamma appeared to be compartmentalized to the lung of these patients in that their blood mononuclear cells spontaneously released little or no IFN gamma (P less than 0.02, compared to sarcoidosis lung mononuclear cells) and no IFN gamma was detected in their serum. Both lung T lymphocytes and alveolar macrophages contributed to the spontaneous release of IFN gamma by lung mononuclear cells from sarcoid patients; purified preparations of T lymphocytes and alveolar macrophages from these patients spontaneously released similar amounts of IFN gamma (56 +/- 21 and 32 +/- 11 U/10(6) cells per 24 h, respectively, P greater than 0.3). At least one role for IFN gamma in the pathogenesis of sarcoidosis appeared to be related to activation of alveolar macrophages, as alveolar macrophages recovered from patients with active disease spontaneously killed [3H]uridine-labeled tumor cell targets (17.7 +/- 4.5% cytotoxicity compared with 2.8 +/- 0.9% in normals, P less than 0.02) and purified IFN gamma enhanced the ability of alveolar macrophages from sarcoidosis patients with inactive disease to kill similar targets (P less than 0.001, compared to alveolar macrophages cultured in medium alone). Treatment of sarcoid patients with corticosteroids, a therapy known to suppress the activity of the disease, caused a marked reduction in the level of spontaneous IFN gamma release by lung mononuclear cells compared with untreated patients (P less than 0.02), which suggests that the effectiveness of corticosteroid therapy in controlling active pulmonary sarcoidosis may, at least in part, be due to suppression of IFN gamma release.

Migration inhibitory factors and macrophage differentiation

It has been described before that only certain types of macrophages are capable to respond to lymphokines and that only certain macrophage phenotypes were able to migrate and to respond to migration inhibitory factors (MIF). With respect to the dissociation of MIF activities from a series of other biological activities, and with regard to the phenotype-associated response of macrophages to MIF it was asked: What are the characteristics of the MIF-responsive macrophage phenotype and what are the functional changes induced by MIF on macrophages in addition to inhibition of random migration? Bone marrow-derived macrophages on day 6 of culture were separated by hypotonic Percoll density gradient centrifugation into three distinct bands and analyzed for a variety of functions. It was found that migrating and MIF-responsive macrophages accumulate at a certain density. These macrophages were further characterized by monoclonal antibodies generated against murine macrophage phenotypes. One marker was found to be preferentially expressed by MIF-responsive macrophages. In order to study the inducibility of MIF responsiveness, bone marrow-derived macrophages on day 16 of culture which were poorly migrating and did not respond to MIF were induced to proliferate by the addition of L cell-conditioned medium. After proliferation had subsided, MIF sensitivity was restored. The effects of MIFs other than migration inhibition, on a number of functions which had been mapped within the cell cycle, were investigated. It was found that MIF acts anti-proliferative on "young", cycling macrophages. Non-cycling, mature macrophages were shifted to a state characterized by a decreased expression of transglutaminase and plasminogen activator and an increase of certain phenotypic surface markers. It is concluded that MIFs are differentiation-inducing signals, acting on the generation of macrophages from precursors but also in the recruitment of terminally differentiated macrophages to "inflammatory" type of macrophages which are functional in the induction of immune responses.

Selection of the delayed hypersensitivity T effector and T suppressor cell response by antigen-presenting macrophages

The T effector lymphocytes of delayed type hypersensitivity reactions (TDH) are regulated by a complex T suppressor (Ts) cell circuit. Induction of TDH cells requires Ia+ adherent cells as antigen-presenting cells. Little is known about the antigen presentation of the induction of Ts cells. We describe an experimental model in which TDH and Ts cells are induced separately by different antigen-presenting macrophages grown from bone marrow stem cells. Bone marrow derived macrophages grown in L cell-conditioned medium for various periods and labeled with 2,4-dinitrobenzene sulfonic acid differ in their ability to induce TDH and Ts cells in vitro. The functional activity of the two T subpopulations was assessed in vivo by epicutaneous challenge or sensitization with 2,4-dinitrofluorobenzene of mice receiving the in vitro educated cells. Ear swelling or suppression of swelling was recorded. It could be shown that 5-7 day bone marrow-derived DNP-labeled macrophages preferentially induced Thy 1+ Lyt 1+ antigen-specific TDH cells; 7-10 day old antigen-presenting bone marrow-derived macrophages induced preferentially Thy 1+ Lyt 2+ antigen specific Ts cells. Characterization of various phenotypic markers revealed different surface antigen expression and functional differences such as MIF responsiveness or transglutaminase activity on the two macrophage populations. These data support the concept that activation of the Ts regulatory circuit may require antigen presentation by specialized antigen presenting cells, characterized by certain surface and functional markers and different from those inducing preferentially TDH cells.

Selective induction of delayed hypersensitivity T-effector and T-suppressor lymphocytes in vitro by haptenized bone marrow-derived macrophages

The role of various subpopulations of antigen-presenting macrophages in the induction of T-lymphocyte subpopulations has been difficult to study in the past. We have used an in vitro system of bone marrow cell culture both to induce T-effector (TDH) and T-suppressor (Ts) cells active in delayed-type hypersensitivity. Bone marrow-derived macrophages (BM-MA) grown in Teflon bag cultures were allowed to attach to culture dishes and were pulse-labeled with 2,4-dinitrobenzene sulfonate (DNBSO3). Spleen cell lymphocytes from nonsensitized BALB/c mice were cocultured with antigen-pulsed or control BM-MA for 3 days. The lymphocytes were harvested, and injected iv into BALB/c mice which were challenged within 1 hr after injection by painting the right ear with 2,4-dinitrofluorobenzene (DNFB, effector test) or sensitized with DNFB on 2 days following iv injection of the cells and challenged 5 days later (suppressor test). Ear swelling was measured 24 hr later to assess the effector or suppressor function of the in vitro educated lymphocytes. BM-MA grown for 5 days (BM-MA 5) in L-cell conditioned medium induced only TDH cells (Thy 1+, Lyt 1+2-) whereas BM-MA grown for 10 days in conditioned medium induced only Ts cells (Thy 1+, Lyt 1-2+). In both cases, induced TDH and Ts cells were antigen specific. Functionally, induced Ts cells suppressed the afferent limb of the delayed response. When DNP-BM-MA 5 and DNP-BM-MA 10 were used to induce TDH or Ts cells in vivo by subcutaneous or intravenous injection respectively, only BM-MA 5 were able to sensitize recipient mice. Both 5- and 10-day macrophage populations induced Ts cells in vivo. Functionally, these Ts cells appeared to act on the efferent limb of the delayed reaction. We conclude that different populations of antigen-presenting macrophages can preferentially induce TDH or Ts cells, perhaps depending on antigen presentation in association with class II antigens or on the functional state of the antigen-presenting cell.

Strain variation in interferon gamma production of BCG-sensitized mice challenged with PPD II. Importance of one major autosomal locus and additional sexual influences

Interferon-gamma (IFN-gamma) production in BCG-sensitized mice challenged with PPD was examined in the sera from BALB/c and C57BL/6 mice. C57BL/6 mice produce about ten times more IFN-gamma than BALB/c mice. Studies on F1, F2, and backcross generations indicate that one partially dominant autosomal locus is involved. Furthermore, females consistently produce more IFN-gamma than males in all of these crosses, though the X chromosome cannot be held responsible for this.

Accessory cell function of liver granuloma macrophages of Schistosoma mansoni-infected mice

In murine schistosomiasis mansoni, the inflammatory macrophage comprises 30% of the granuloma which forms around parasite eggs in the tissue. These granuloma macrophages (GR-Mphi) displayed dense Fc and C3 receptors, and about 50% expressed H-2I region-encoded determinants (Ia antigens). These GR-Mphi were able to effectively reconstitute the burro erythrocyte-specific immunoglobulin M and G antibody response of primed macrophage-depleted spleen cells. However, in contrast to splenic macrophages, GR-Mphi gave only minimal reconstitution of the primary immunoglobulin M response. The reconstitution of the T-cell proliferative response to L-glutamic60-L-alanine30-L-tyrosine10, an antigen under Ir gene control, was also observed when GR-Mphi were added to purified lymph node T-cells. The addition of a monoclonal antibody recognizing a determinant on the Ia complex effectively blocked L-glutamic60-L-alanine30-L-tyrosine10 presentation by GR-Mphi. These studies demonstrated that inflammatory GR-Mphi could function as antigen-presenting cells and that this accessory function was mediated by H-2I region gene products.

Regulation of plasminogen activator secretion, interferon induction and proliferation in murine macrophages

The purpose of this work was to study the interrelationship of proliferation and secretion of plasminogen activator (PA) and interferon (IFN) by murine macrophages. For induction of macrophage proliferation and secretion of PA, concanavalin A (Con A) was used. Secretion of IFN was induced by polyinosinic polycytidylic acid complex. The glucocorticoid dexamethasone acetate (DA) (10(-6)-10(9) M) inhibited Con A-stimulated secretion of PA and synthesis of DNA as evaluated by incorporation of [3H]thymidine. DA did not inhibit IFN induction. Preincubating macrophages with DA for 45 h reduced basal proliferation and secretion of PA but did not reduce responsiveness to Con A. Also retinoic acid, a modulator of carcinogenesis was used in inhibition studies because of its known antagonistic effects on lymphocyte mitogenesis. In macrophages a biphasic effect of retinoic acid (1 X 10(-5) - 5 X 10(-5)M) was found: (a) inhibition of DNA synthesis and secretion of PA during the first 45 h of incubation, and (b) enhancement of DNA synthesis (but not PA secretion) after 72 h. Secretion of IFN was not affected. It is suggested that secretion of PA but not IFN is linked to cell cycle traverse of macrophages.

Sendai virus-specific T cell clones II. Induction of interferon production by Sendai virus-specific T helper cell clones

Interferon (IFN) was detected upon co-culture of cloned Sendai virus (SV)-specific T lymphocyte with SV-presenting syngeneic stimulator cells. The antiviral activity was defined as IFN-alpha, beta. The T cell clones, upon contact with antigen-presenting stimulator cells, stimulated adherent cells present in the stimulator cell population to secrete IFN. Induction of IFN production was independent from interleukin 2 production by the T cell clones.

Regulatory effect of monocytes on T cell proliferative responses to oral microbial antigens

Mononuclear cell preparations isolated by Ficoll-Hypaque centrifugation from human peripheral blood were found to vary considerably in the number of monocytes they contained (mean, 20.3%; range, 13 to 33%). The regulatory role of monocytes in T cell proliferative responses to sonic extracts of a panel of oral microorganisms was therefore investigated. T cells were fractionated by anti-immunoglobulin chromatography and depleted of monocytes by treatment with a monoclonal anti-human Ia-like (DR locus antigen) antibody and complement. Purified populations of monocytes were obtained by extensive adherence procedures. The resultant cell populations were greater than 95% pure, as judged by indirect immunofluorescence on a fluorescence-activated cell sorter. Monocyte-depleted T cells failed to respond by proliferation to the nonoral antigen tetanus toxoid, as well as to any oral microorganism, but retained responsiveness to phytohemagglutinin. Readdition of monocytes in final concentrations of from 5 to 15% resulted in the restoration of maximal T cell proliferation. Monocytes in greater numbers suppressed T cell responses to all sonic extracts tested.

Heterogeneity of macrophages in response to lymphokines and other signals

Macrophages which are intimately involved in acute and chronic inflammatory reactions are functionally heterogeneous not only with regard to the expression of constitutive functions but also in their response to lymphokine signals. The biological basis of this heterogeneity is poorly understood. Whether we are dealing with true subpopulations or with intermediately stable phenotypes has not been resolved. To study these questions we adopted a bone marrow liquid culture system in which bone marrow cells--in the presence of a colony-stimulating factor--proliferate and differentiate into macrophages. This culture system was taken here as a model to study the expression of various functions by macrophages in the course of maturation. Several tests were performed daily and in parallel from the same batch of cells. It was found that certain functions were expressed early and were also characteristic for mature macrophages such as Fc receptors, phagocytosis of latex beads and unspecific esterase. Other functions appeared and disappeared in an ordered sequence, such as the response to macrophage migration inhibitory factor and chemotactic factor as well as the production of interferon and plasminogen activator. The time course of functional expression was strongly dependent on proliferation of precursor cells as well as on proliferation of differentiated macrophages. It is concluded that the transient phenotypic expression of functions during differentiation is the basis for the functional heterogeneity of macrophages.

Involvement of monokines in antigen- and lectin-induced human lymphokine production

To analyze the role of monocytes/macrophages (Mø's) in the activation of human lymphocytes, suspensions enriched in T cells and markedly depleted of Mø's were prepared. The Mø-depleted cells challenged by tuberculin did not elaborate the lymphokine, leukocyte migration inhibitory factor (LIF). This reduction in LIF production was negatively correlated to the proportion of residual Mø's being complete in the presence of less than 2% Mø's. In contrast, the LIF response to the polyclonal activator, phytohemagglutinin A, was unimpaired by Mø depletion. LIF production of the Mø-depleted cells could be fully reconstituted by addition of conditioned media obtained from Mø cultures, especially if stimulated by the Mø-activating agent, phorbol myristate acetate. This effect was dose-dependent and could be ascribed to molecules of molecular weights 80K and 12K, respectively.

Modulation of macrophage functions by lymphokines

Macrophage migration inhibitory factors (MIFs) of mouse and guinea pig have been thoroughly characterized with regard to molecular weight and isoelectric points. Several molecular weight species have been identified. In a comparative study with purified MIFs it was found that these molecules were distinct from a series of other lymphokines, particularly so from macrophage activating activities. Investigations on the molecular weight heterogeneity of MIF have led us to a transglutaminase-like activity which was found to be expressed in certain subsets of macrophages. The question whether low molecular weight factors are polymerized by this enzyme to oligomers is further investigated. Studies on the induction by lymphokines of interferon and plasminogen activator revealed a great heterogeneity of responding macrophages. In studies on the biological basis of the functional heterogeneity of macrophages, the question was investigated whether the heterogeneity was due to different macrophage subpopulations or to intermediate relatively stable phenotypes on their way to maturity and senescence. To approach this question, the bone marrow liquid culture system was used as a developing system. Our data are summarized in a unifying model which takes into account the different constitutive and inducible functions during the cell cycle. Accordingly, lymphokines may act either as differentiation signals, as mitogens or activating signals.

Dissociation between tumour cell cytostatic and immuno-suppressive capacity of human monocytes activated with lymphokines

Activation of monocytes with lymphokines from BCG-stimulated lymphocytes increased the capacity to inhibit DNA-synthesis in a tumour cell line (NHIK 3025) at all stages of monocyte maturation in vitro. However, the capacity of monocytes to suppress DNA-synthesis in mixed lymphocyte cultures (MLC) was reduced, indicating a dissociation of the immuno-suppressive and tumour cell cytostatic functions of lymphokine-activated monocytes. Supernatants of lymphokine-activated monocytes inhibited DNA synthesis in the tumour cell line, but not in MLC. Monocytes from donors with a strong tuberculin reaction produced supernatants with a stronger cytostatic activity than monocytes from donors with a weak tuberculin reaction. By in vitro maturation, even the later monocytes acquired ability to produce supernatants that were strongly inhibitory to tumour cells.

Gamma interferon production by combinations of human peripheral blood lymphocytes, monocytes, and cultured macrophages

Mitogen-induced interferon (IFN) production was studied using human peripheral blood mononuclear cells and subpopulations of lymphocytes, monocytes, and cultured macrophages. Cell populations were prepared in suspension to permit quantitative analysis of the interactions among different cell types. After stimulation by staphylococcal enterotoxin A, nylon column-purified lymphocytes produced only 5% as much IFN as the peripheral blood mononuclear cells from which they were prepared. When lymphocytes were supplemented with as little as 2% monocytes, IFN production increased two- to eightfold; with the addition of up to 20% monocytes, IFN production increased further, to levels approximating those of peripheral blood mononuclear cells. Monocytes alone produced no or very little IFN. Macrophages were derived from monocytes by culturing in vitro for 7 days. The addition of 2 to 5% autologous macrophages augmented IFN production to the same extent as 2 to 5% monocytes. However, more macrophages consistently resulted in less, rather than more, IFN, so that lymphocytes with 20% monocytes produced three- to eightfold more IFN than did lymphocytes with 20% macrophages. Thus, whereas the addition of monocytes over a broad dose-response range (2 to 20%) progressively augmented IFN production, macrophages showed an optimal effect at 2 to 5%, with higher percentages being inhibitory. The IFN induced by stimulation with staphylococcal enterotoxin A was characterized as IFN-gamma by its resistance to neutralization by antibody to IFN- alpha and its inability to induce antiviral protection in embryonic bovine trachea cells.

Similarities of murine gamma interferon and the lymphokine that renders macrophages cytotoxic

Murine spleen lymphoid cells treated with insoluble (Sepharose bound) concanavalin A elaborate Gamma (immune) interferon (IFN-gamma) and macrophage activation factor (MAF) into the culture medium. Similarly, MAF is produced by T cells with other IFN-gamma inducers. MAF induces resting (noncytotoxic) macrophages to become tumoricidal. We have compared various physicochemical properties of MAF and INF-gamma, their neutralization by antibody to IFN-gamma, and their induction period. In these parameters, induction of antiviral activity was compared to induction of macrophage tumoricidal activity. All of the parameters studied have given results that demonstrate close similarity in the physical properties, molecular characteristics, and biological reactivities of the two lymphokines, and this similarity suggests that these two lymphokines reside in the same molecule. This conclusion would include that IFN-gamma, like IFN-alpha and IFN-beta, is capable of activating macrophages to become cytotoxic toward tumor cells.

Modulation of suppressor mechanism in allergic contact dermatitis. IV. Selective inhibition of suppressor T-lymphocytes by serum obtained from Corynebacterium parvum treated mice

We have previously shown that Corynebacterium parvum treatment reduced tolerance induced by intravenous injection of 2,4-dinitrobenzene sulfonic acid (DNBSO3) or by sensitizing BALB/c mice with a supraoptimal dose of 2,4-dinitrofluorobenzene (DNFB). Further analysis by transfer experiments revealed that the generation and/or functional expression of suppressor T-lymphocytes (Ts-cells) was inhibited in both tolerance models. Inhibition of Ts-cells was not entirely correlated with suppression of mitogen induced lymphocyte proliferation mediated by C. parvum activated macrophages. In this investigation we studied the effect of serum obtained at various times after C. parvum injection on tolerance and Ts-cells in DNFB contact allergy. Serum obtained 6 and 24 hr, however, not 72 hr after C.parvum injection inhibited Ts-cells, induced by DNBSO3 and tested by transfer to naive recipients, as efficiently as C. parvum itself. The serum had following characteristics: (1) It inhibited the functional expression of Ts in the recipient animal. (2) It inhibited tolerance induction by an epicutaneous supra-optimal dose of DNFB. (3) It did not inhibit the induction and functional expression of T-effector cells of delayed hypersensitivity (TDH-cells) as shown by transfer experiments. (4) The Ts-inhibitory factor was heat resistant (56 degrees C), not destroyed or lost by dialysis against tris-glycine buffer pH 2 and could not be detected in the serum of NMRI-mice injected 24 hr before with C parvum. (5) The C parvum serum did not significantly increase the spleen weight or suppress mitogen-induced spleen lymphocyte proliferation. The nature of this Ts-cells inhibitory factor is unknown, although the results suggest that cortisone or transfer of bacteria are not responsible. Factors mediating selective inhibition of Ts-cells may be of important regulatory function in delayed type hypersensitivity.

Transglutaminase as a marker for subsets of murine macrophages

Transglutaminase was detected either at the single cell level by fluorescent staining with dansylcadaverine or in cell homogenates by incorporation of [14C] putrescine into alpha-casein. In the mouse it was found that erythrocytes, granulocytes, thymocytes or lymphocytes with or without concanavalin A stimulation were negative in the fluorescence test. Normal peritoneal washout macrophages and peritoneal exudate cells stained positive to varying degrees (induced with mineral oil 64%, with thioglycollate 50%, with proteose peptone 22%, normal washout 1%). Macrophages from bone marrow liquid cultures were 20% positive at day 3 and 100% at day 17. Promonocytes and monocytes were negative. Positively stained cells also phagocytosed opsonized sheep erythrocytes. The degree of staining varied considerably in the macrophage-like cell lines IC21 (100%), J774.2 (75%), P388-D1 (50%). This result and those from autoradiography studies indicate that expression of transglutaminase is not associated with the S-phase of the cell cycle. The fluorescence test correlates quantitatively with the [14C] putrescine incorporation test. The enzyme is Ca2+-dependent and appears neither to be on the outer cell surface nor being released into the culture medium. Circumstantial evidence indicates that it is also not compartmentalized in cytoplasmic vesicles. While the induction and modulation of enzyme expression is still under study, it is concluded that transglutaminase is a new marker for macrophages of a certain differentiation or activation state.

Production of immune interferon (type II) in cocultures of mouse peritoneal macrophages and syngeneic tumour cells

Mouse peritoneal macrophages were activated by coculture with syngeneic methylcholanthrene-induced sarcoma cells [7], which grow as an ascites tumour in C3D2 mice [3]. During 4-5 days of cocultivation tumour cells progressively died, leaving highly activated macrophages. Cell-free supernatant harvested from the cultures contained larger amounts of interferon than either macrophages or tumour cells cultivated alone. Peak activity of interferon occurred on day 2. Non-adherent cells cultivated together with tumour cells did not produce interferon. Removal of all non-adherent cells from macrophage cultures and host cells from tumour cell suspension did not abolish interferon production. The macrophages thus seem to be the interferon-producing cells, but the possibility that the very few remaining lymphocytes may cooperate with the macrophages in interferon production cannot be totally ruled out. The interferon produced could not be inactivated by antibodies against virus-induced interferon and was destroyed by treatment at pH 2, indicating that the interferon was not of the alpha or beta type.

Modulation of suppressor mechanisms in allergic contact dermatitis: 2. Inhibition of suppressor T-lymphocytes by Corynebacterium parvum

Pretreatment of BALB/c mice with Corynebacterium parvum inhibited the induction of tolerance to the contact sensitizing agent 2,4-dinitrofluorobenzene induced by intravenous injection of DNBSO3. The suppressive effect on tolerance induction has further been analyzed by adoptive transfer experiments. Injection of C. parvum intraperitoneally (0.7-2.8 mg/mouse) before injection of the tolergen inhibited the generation of T-suppressor cells as shown by transfer of spleen cells from the tolerized donor to naive recipients. Pretreatment of the recipients of the suppressor T-cells from tolerized animals with C. parvum also inhibited the function of these cells in the recipient animals. Time-kinetic experiments suggested that more than one mechanism appeared to be responsible for the tolerance induced by DNBSO3; C. parvum (probably via activated macrophages) suppressed tolerance which is mediated by T-suppressor lymphocytes. These results suggest that T-suppressor lymphocytes may--similarly as T-helper cells--be modulated by an activated monocytic-phagocytic system.

Modulation of suppressor mechanisms in allergic contact dermatitis: 1. Effect of C. parvum on the induction phase of contact allergy

The effect of a pretreatment with corynebacterium parvum (C. parvum) on contact allergy in BALB/c mice was studied. Mice sensitized with 50 microliter (supraoptimal dose) 2.4-dinitrofluorobenzene (DNFB, 0.5%) showed a suppressed response as measured by ear swelling after painting the right ear with 0.3% DNFB in comparison to an allergic response obtained with an optimal sensitization dose (15 microliter DNFB 0.5%). By transfer of spleen cells from donors sensitized with a supraoptimal or an optimal dose to recipients either challenged ro sensitized shortly afterwards with DNFB it could be shown that less functionally active immune T-lymphocytes of the delayed hypersensitivity type and significantly more suppressor T-cells were induced in supraoptimally sensitized mice in comparison to the optimally sensitized animals. Intraperitoneal injection of C. parvum (2.8 mg/mouse) one week before sensitization enhanced the contact allergic response in mice sensitized with a supraoptimal dose of DNFB, with little effect on the response in optimally sensitized animals. Further analysis of this enhancement in transfer experiments showed that C, parvum selectively suppressed the generation and/or functional expression of T-suppressor cells and, probably by this mechanism, increased the number of functionally active T-immune lymphocytes. It is proposed that possibly by activation of the immune system C. parvum will suppress suppressor cells in contact allergy and by this mechanism might facilitate sensitization to the contact allergen.

Mechanisms in in vivo release of lymphokines. III. Separation of gamma-interferon (IFN gamma) from cytotoxicity in inbred strains of mice

Inbred strains of mice sensitized with BCG and challenged with old tuberculin (OT) vary in their capacity to release IFN gamma and MIF into circulation. Experiments were performed to correlate the presence of IFN gamma with that of the cytotoxic effect in an attempt to learn whether these two activities in the sera may be separated. Sera from eight inbred strains were obtained at times after challenge and assayed for IFN and for cytotoxic activity. A correlation did not exist between the titers of IFN gamma and the levels of cytotoxicity, i.e. sera from RF/J mice without detectable titers of IFN gamma had cytotoxic activity, while sera from C57BL/KsJ mice that had titers of IFN gamma were not cytotoxic. Regulation of IFN gamma titers could be achieved by administration of complete Freund's adjuvant to BCG sensitized mice. However, similar differences were not detected in cytotoxic activity. Therefore, IFN gamma may be released, or the activity of IFN gamma may be expressed in the circulation, in the absence of cytotoxicity.

Studies of the producer cell of herpes simplex virus-induced interferon in mouse spleen cell cultures

The producer cell of type I interferon was studied in spleen cell cultures of C57BL/6 mice stimulated by inactivated Herpes Simplex Virus (HSV). Interferon production was not abolished by pretreatment of the spleen cells by anti-theta serum plus complement. The producer cell of interferon was not removed by plastic adherence and was not destroyed by the addition of silica. It was present in spleens of 3 day old C57BL/6 mice and in spleens of nu/nu mice. It was not inactivated by treatment of nu/nu spleen cells by anti-theta serum plus complement. HSV-induced interferon production was abolished by passage of the spleen cells through nylon wool columns and by irradiation (1000 R) of the spleen cells. Collectively these data suggest that in murine spleen cell cultures type I interferon is produced by B cells. However, our data do not allow to rule out that the interferon producing cell may be an immature macrophage or an immature T cell.

Sequential expression of functions during macrophage differentiation in murine bone marrow liquid cultures

In the presence of a colony-stimulating factor, murine bone marrow cells proliferate and differentiate into macrophages. This culture system was taken as a model to study the expression of various functions by macrophages in the course of maturation. Several tests were performed daily and in parallel from the same batch of cells. It was found that certain functions were expressed early and were also characteristic for mature macrophages such as Fc receptors, phagocytosis of latex beads and unspecific esterase activity. Other functions appeared and disappeared in an ordered sequence, such as the response to macrophage migration inhibitory factor and chemotactic factor as well as the production of interferon and of plasminogen activator. The time course of functional expression was strongly dependent on proliferation of precursor cells as well as proliferation of differentiated macrophages. It is suggested that the phenotypic expression of functions during differentiation is the basis for the functional heterogeneity of macrophages.

Role of adherent cells in graft-versus-host-induced suppression of the humoral immune response

Experiments were performed to investigate the role of adherent (A) cells in graft-versus-host (GVH)-induced immunosuppression. GVH reactions (GVHR) were induced in adult F1 hybrid mice by intravenous injections of parental lymphoid cells. Spleen cells (SC) from mice experiencing a GVHR (GVH mice) were stimulated with phytohaemagglutinin (PHA), concanavalin (Con A), and lipopolysaccharide (LPS). SC taken in the early phase of the GVHR (early GVHR) responded normally to LPS but did not respond to PHA and Con A. SC taken in an advanced phase of the GVHR (advanced GVHR) did not respond to PHA, Con A, or LPS. The influence of A cells from GVH mice (GVH-A cells) on the response of normal non-adherent cells to sheep erythrocytes (SRBC), PHA, and LPS was investigated. A cells from early GVHR, used in appropriate numbers, stimulated the responses to SRBC and to PHA; in excess they inhibited both responses. They had no effect on the response to LPS. A cells from advanced GVHR, even in low numbers, suppressed the responses to SRBC, PHA and LPS. The lymphoregulatory activities of GVH-A cells seemed to be mediated by soluble factors. The results indicate that the GVHR evokes complex non-specific regulatory interactions between A cells and lymphocytes.

Human peripheral null lymphocytes. II. Producers of type-1 interferon upon stimulation with tumor cells, Herpes simplex virus and Corynebacterium parvum

Human blood lymphocytes, exposed for 6 to 24 h in vitro to tumor cells (K 562, IGR3, L1210), Herpes simplex virus type 1 (HSV) or Corynebacterium parvum (CP), produced high levels of anti-viral activity which was identified as type-1 interferon (IF). In mixed lymphocyte tumor cell cultures (MLTC), the generated type-1 IF was definitely shown to originate from the lymphocytes and not from the tumor cells. Supplementation of leukocyte cultures with 10% fetal calf serum instead 10% human AB serum had little influence on tumor cell-induced IF production, but strongly reduced CP-induced IF production. Lymphocyte fractionation procedures involving iron/plastic treatment, nylon wool columns, Ig-anti-Ig columns and rosette (E, EA) separation led to the identification of null cells as highly efficient producers of type-1 IF. T cells obtained by different ways (E-rosette sedimentation, passage through 1 nylon and 2 Ig-anti-Ig columns, or thoracic duct lymphocytes) were poor IF producers in response to tumor cells, HSV and CP, but secreted anti-viral activity when stimulated with phytohemagglutinin. In MLTC, the level of generated type-1 IF roughly stimulated with phytohemagglutinin. In MLTC, the level of generated type-1 IF roughly paralleled nautral killer (NK) cell activity. Evidence is presented that type-1 IF can be produced by an Fc receptor-negative null cell subset, whereas NK activity requires Fc receptor-positive cells. It is suggested that production of type-1 IF represents one of the earliest functions in the differentiation process of mononuclear phagocytes and is likely to develop before the appearance of Fc receptors, diffuse esterase staining and latex phagocytosis.

Immune interferon secretion as an expression of immunological memory to transplantation antigens: in vivo generation of long-lived, recirculating memory cells

Leukocytes from C57Bl/6 mice immunized against DBA/2 strain antigens by intraperitoneal injection of mastocytoma P 815 cells produced, when stimulated in the mixed leukocyte reaction assay with DBA/2 spleen cells, an earlier and more intense secretion of immune interferon than leukocytes from untreated mice. This secondary-type interferon response was independent of cell proliferation. The memory phenomenon was induced by long-lived, recirculating lymphocytes found in spleen, lymph nodes and thoracic duct, but not in the thymus. Memory cells could be recruited into inflammatory sites. They were shown to be specific for H-2 alloantigens, although some cross-reactivity with stimulating cells bearing unrelated H-2 antigens was observed. The possible anti-tumor, antiviral and immunoregulatory roles of this memory phenomenon, and its significance in transplantation immunity are discussed.