Morphological,cytochemical, functional,and proliferative characteristics of four murine macrophage-like cell lines

The aim of the present study was to obtain objective data on the morphology and quantitative information about other characteristics of murine macrophage-like cell lines J774.1, PU5-1.8, WEHI-3, and P388-D1, and to compare the findings with those in resident and exudate macrophages collected directly from mice. Fetal fibroblasts were included to serve as controls.Evaluation of the morphological data showed that the cell lines J774.1 and WEHI-3 are almost identical in most respects, that the cells of P388-D1 differ widely from both of the former lines, and that the morphometric parameters of cell line PU5-1.8 occupy an intermediate position. The cells of the P388-D1 line show the most similarity to resident and exudate macrophages, and cell lines J774.1 and WEHI-3 the least. Fetal fibroblasts had divergent values for all morphometric parameters. Good correspondence was found when the quantitative data obtained by morphometric analysis of the cells in question were compared with the morphological pictures.No gross differences as to cytochemical characteristics were found between the cells of the four cell lines, except for 5′-nucleotidase activity. The occurrence of IgG receptors and the ingestion of EIgG were also similar, but the percentage of cells with C3b receptors was much lower in two of the cell lines (WEHI-3 and P388-D1) and the level of EIgMC ingestion was very much higher in one (J774.1) compared with both the other cell lines and the resident and exudate macrophages. The ingestion of opsonized bacteria and latex varied widely within and between the cell lines. Quantitative data on the binding of monoclonal antibodies by the cells of the macrophage cell lines and the resident and exudate macrophages showed a wide variation. The doubling time of the cell lines is on average 1 day; distinct differences were found between these lines with respect to the lag-time of proliferation after replating.Cluster analysis and statistical analysis of morphological and other characteristics gave insight into the degree of resemblance between the cells of the four cell lines on the one hand and the resident and exudate macrophages on the other.     

Immunostimulatory effect of spinach aqueous extract on mouse macrophage-like J774.1 cells and mouse primary peritoneal macrophages

We herein report the immunostimulatory effect of spinach aqueous extract (SAE) on mouse macrophage-like J774.1 cells and mouse primary peritoneal macrophages. SAE significantly enhanced the production of interleukin (IL)-6 and tumor necrosis factor-α by both J774.1 cells and peritoneal macrophages by enhancing the expression levels of these cytokine genes. In addition, the phagocytosis activity of J774.1 cells was facilitated by SAE. Immunoblot analysis revealed that SAE activates mitogen-activated protein kinase and nuclear factor-κB cascades. It was found that SAE activates macrophages through not only TLR4, but also other receptors. The production of IL-6 was significantly enhanced by peritoneal macrophages from SAE-administered BALB/c mice, suggesting that SAE has a potential to stimulate macrophage activity in vivo. Taken together, these data indicate that SAE would be a beneficial functional food with immunostimulatory effects on macrophages.     

Induction of ornithine decarboxylase in macrophages by bacterial lipopolysaccharides (LPS) and mycobacterial cell wall material

Lipopolysaccharide from $\text{E. Coli}$ (LPS) and BCG cell walls (BCGcw) are recognized immunoadjuvants that directly stimulate some macrophage functions. The macrophage cell line J774.1 and peritoneal exudate cells (PEC) from mice can be stimulated by LPS or other adjuvants $\text{in vitro}$ to synthesize and release protein factor(s) that activate thymus-derived lymphocytes. We have utilized J774.1 cells and PEC to demonstrate that an increase in ornithine decarboxylase (ODC) activity is a marker of early biochemical changes in adjuvant-stimulated macrophages. BCGcw and LPS increased ODC within 2 hours in J774.1 cells as well as murine peritoneal exudate macrophages. Maximal increases in ODC were detected 4 hours after the addition of adjuvants to J774.1 cells. The marked increases (12–23 fold) in ODC observed with BCGcw (20 μg/ml) did not appear to involve an effect on cell proliferation which was suppressed by this adjuvant. Cycloheximide inhibited the induction of ODC by LPS and BCGcw in the macrophage cell line. Evidence that the induction of ODC may be promoted by an increase in cyclic AMP was provided by experiments demonstrating that prostaglandin E₁ (PGE₁) and 8-bromo-adenosine-3′:5′-monophosphate (8Br-cyclic AMP) can mimic the effects of LPS and BCGcw in J774.1 cells. These observations indicate that one of the early biochemical changes in macrophages promoted by adjuvants is an induction of ODC.     

LPS-or 8Br-cyclic AMP-induced production of T cell-activating factor(s) in macrophage tumor cell line J774.1.

The macrophage tumor cell line J774.1 replaced the function of normal macrophages in the induction of polyclonal killer T cells with 2-mercaptoethanol. J774.1 does not normally release soluble factor(s) which we have shown to be responsible for the differentiation of T cells to killer T cells. However, stimulation of J774.1 with LPS induced soluble factor(s) for T cell activation. An optimum concentration of LPS for the production of soluble factor(s) was 1 to 10 microgram/ml, which completely inhibited growth of the tumor cells. The production of soluble factor(s) was observed within 6 hr after LPS stimulation and reached its maximum level at 24 hr. Incubation of the cell line with 8Br-cyclic AMP and theophylline induced soluble factor(s), suggesting that LPS stimulation induced an increase in intracellular cyclic AMP which leads to the synthesis of soluble factor(s).     

Control of lipoprotein lipase secretion in mouse macrophages

The regulation of secretion of lipoprotein lipase (LPL) was studied in in vitro-derived mouse bone marrow macrophages (BMM), peritoneal exudate and resident macrophages and in the macrophage-like tumor cell line J774.1. BMM in cultures initiated with low concentrations of bone marrow cells (LC-BMC cultures) secrete more LPL per cell than BMM in cultures initiated with high concentrations of bone marrow cells (HC-BMC cultures). The suppressed state of LPL secretion in HC-BMC cultures could be alleviated by the addition of a colony-stimulating factor source (L-cell-conditioned medium; L-CM) onto the culture medium or exchanging the medium of HC-BMC cultures with medium from LC-BMC cultures for short periods (4 h). Addition of L-CM increased LPL secretion also in LC-BMC cultures. Addition of L-CM to fresh culture medium had little or no effect, suggesting that, in addition to requirement for L-CM, optimal expression depended also on factors released by the growing cells, probably providing optimal growth conditions. L-CM enhanced LPL secretion by thioglycollate-elicited peritoneal macrophages and had no effect on LPL secretion by resident peritoneal macrophages. Secretion of LPL from adherent J774.1 cells showed a biphasic effect. Secretion increased with cell density up to the point when growth inhibition was observed. In dense cultures in which cell proliferation was almost arrested, LPL secretion was remarkably suppressed (80-90%). Change of medium of dense cultures to fresh medium or medium conditioned by sparse cultures (for the last 4 h of culture) led to enhancement of LPL secretion to levels similar to those optimally expressed by sparse cultures. L-CM did not enhance LPL secretion from J774.1 cells. Dense cultures of both BMM and J774.1 cells did not contain a stable inhibitor of LPL secretion and medium from sparse cultures did not contain an inducer of LPL secretion. The data suggest that proliferating macrophages secrete large amounts of LPL, whereas in nonproliferating, quiescent cells, this activity is much reduced. L-CM enhances LPL secretion in quiescent BMM and peritoneal exudate cells to levels expressed by proliferating cells. Since this effect is already expressed after a 4 h incubation period, it is not dependent on cell cycling but could be one of the early responses to this macrophage mitogen. In J774.1 cells, a change of medium is a sufficient signal for enhancement of LPL secretion in quiescent cells.     

High cytotoxic activity against herpes simplex virus type 1 infected targets found in murine peritoneum

Unelicited murine peritoneal cells (PC) were found to efficiently lyse the natural cytotoxic (NC) cell target, WEHI-164, as well as herpes simplex virus-type 1 (HSV-1)-infected WEHI-164 and 3T3 cells but not the natural killer (NK) target, YAC-1. Lysis by PC of HSV-1-infected WEHI-164 and 3T3 cells required longer culture times than splenic cell lysis of YAC-1 cells. The PCs which lysed these targets were found to be slightly adherent to nylon wool but non-phagocytic, and were not augmented by preincubation with interferon. Also, PC effectors lacked Qa-5 and asialo GM1 markers which are found on splenic NK cells which lysed YAC-1 targets. We found that there was no correlation between peritoneal NC activity and genetic resistance to HSV-1.     

Analysis of the activation of lymphoid cells by mitogens in vitro with limiting dilution methods: adherent peritoneal cells suppress B-cell activation and synergize with WEHI-3 in the activation of T cells by Con A

Adherent peritoneal cells (APC) have often been used as a pure and effective macrophage population. Using partition analysis and small numbers of lymphoid cells activated by mitogens (concanavalin A for T cells (in the presence of TCGF) and LPS + DxS for B cells) we found that APC were accessory cells for T cell activation and growth but were not effective for B cells. Although APC were effective in assisting T-cell mitogenesis, they were not especially efficient. However, when APC were mixed with irradiated WEHI-3 cells (a tissue culture line previously shown to exhibit accessory cell activity in vitro for mitogenic activation T and B cells), the APC and WEHI-3 showed apparent synergy. One reason for failure of APC to assist B-cell mitogenesis was traced to the presence of a suppressor cell population which overcame the accessory cell help given by irradiated WEHI-3 cells to LPS-DxS stimulated murine B cells. It is thus possible to find "helper" effects (synergy of APC and WEHI-3 assisting the mitogenesis of T cells), as well as suppressor effects within the range of cells found in adherent accessory cells.     

A significant part of macrophage-derived growth factor consists of at least two forms of PDGF

The macrophage has been suggested to be responsible for the connective tissue cell proliferation that accompanies most chronic inflammatory responses. One of the secretory products of activated macrophages is MDGF, a growth factor (or factors) for fibroblasts, 3T3 cells, smooth muscle, and vascular endothelium. This report demonstrates that a significant portion of the mitogenic activity for 3T3 cells secreted by cultured human alveolar and peritoneal macrophages is due to a molecule (or molecules) similar to platelet-derived growth factor (PDGF). Two size classes (approximately 37,000-39,000 and 12,000-17,000 daltons) of mitogenically active PDGF-like molecules are detected by two criteria--antigenic similarity with PDGF and ability to compete with 125I-PDGF for high-affinity binding to the PDGF receptor. The presence of mRNA for the B chain of PDGF is demonstrated by Northern analysis, and de novo synthesis of these molecules by activated macrophages is shown by immunoprecipitation of 35S-labeled proteins with anti-PDGF IgG.     

Enhancement of O2- generation and tumoricidal activity of murine macrophages by a monosaccharide precursor of Escherichia coli lipid A

The effects of a monosaccharide precursor of Escherichia coli lipid A (lipid X) on murine macrophages were studied. Lipid X is a diacylglucosamine 1-phosphate bearing beta-hydroxymyristoyl groups at positions 2 and 3. Lipid X, as well as lipopolysaccharide and lipid A, enhanced O2- generation in mouse peritoneal macrophages and a macrophage-like cell line, J774.1, and further induced the tumor-cytotoxic activity of peritoneal macrophages. Elimination of a 1-phosphate or 3-O-beta-hydroxymyristoyl groups are essential for the elevated O2- generation and induction of tumoricidal activity due to lipid X.     

Potent effects of,and mechanisms for,modification of crosstalk between macrophages and adipocytes by lactobacilli

The murine macrophage‐like cell line J774.1 was treated with heat‐killed cells of Lactobacillus GG (LGG) and L. gasseri TMC0356 (TMC 0356). Interleukin (IL)‐6, IL‐12, and tumor necrosis factor‐α were profiled from the J774.1 cells using enzyme‐linked immunosorbent assay methods. The conditioned medium from cultured J774.1 cells was transferred to the preadipocyte cell line 3T3‐L1 (which is a mouse embryonic fibroblast‐adipose‐like cell line). Growth and differentiation of 3T3‐L1 cells were monitored by analyzing lipid accumulation and expression of peroxisome proliferator‐activated receptor (PPAR)‐γ mRNA. The medium conditioned by 3T3‐L1 cells was added to J774.1 cells and the cytokines in the supernatant analyzed. Compared with that of cells exposed to a PBS‐conditioned medium, lipid accumulation in 3T3‐L1 cells was significantly suppressed in a dose‐dependent manner by each medium that had been conditioned with LGG and TMC0356. PPAR‐γ mRNA expression in 3T3‐L1 cells was also significantly downregulated (P < 0.01, P < 0.05, respectively). The conditioned medium of 3T3‐L1 adipose phenotype significantly stimulated production of IL‐6 and IL‐12 in J774.1 cells treated with LGG and TMC0356. These results suggest that lactobacilli may suppress differentiation of preadipocytes through macrophage activation and alter the immune responses of macrophages to adipose cells.     

Biochemical relationship between murine immune interferon and a killer cell helper factor.

Concanavalin A and alloantigen-stimulated mouse spleen cells release into the supernatant at least two distinct antigen-nonspecific factors that enhance the generation of cytotoxic cells in vitro. As previously reported, analysis of the supernatant by ammonium sulfate fractionation, gel filtration, hydroxylapatite chromatography, and hydrophobic chromatographic showed one of the two killer cell helper factors (KHF) to be associated with thymocyte mitogenic factor. This report demonstrates the second KHF to be separable from thymocyte mitogenic factor but inseparable from type II (immune) interferon. In addition, this KHF exhibits the same sensitivity to exposure to pH-2 buffer as does immune interferon. The KHF activity of an unfractionated supernatant, which is greater than of either the TMF-associated or interferon-associated KHF alone, is the result of the additive activities of the two independently acting helper factors.     

Nitric oxide-mediated protection of A. actinomycetemcomitans-infected murine macrophages against apoptosis.

We investigated apoptotic cell death in murine macrophage cell line J774.1 following Actinobacillus actinomycetemcomitans infection. Infected macrophages generally kill bacteria within phagosomes with nitric oxide (NO). Our previous study demonstrated that DNA fragmentation in infected cells increased significantly on addition of S-Methylisothiourea (SMT), a selective inhibitor of inducible NO synthetase (iNOS). The purpose of the present study was to determine the mechanism via which NO affects apoptosis of infected macrophages. J774.1 cells were infected with A. actinomycetemcomitans Y4 at a bacterium/cell ratio of 500:1. The infected cells were then cultured in the presence or absence of SMT (400 microM). Culture supernatant was removed 21 h after the infection to measure LDH activity. Additionally, cellular proteins were extracted from the infected cells and measured for histone-associated DNA fragmentation and caspase-1, -3, -5, -6, -8, -9 activities. LDH activity and DNA fragmentation were significantly elevated by the infection; moreover, levels increased further on addition of SMT. Caspase activity of infected cells, particularly caspase-3, was significantly higher than that of uninfected cells. Furthermore, caspase activity increased on addition of SMT. These findings indicate that NO protects infected J774.1 cells, at least in part, against apoptotic cell death via a decrease in caspase activity.     

Effect of T- and B-lymphocyte mitogens on interactions between lymphocytes and macrophages.

The mitogenic response of murine T cells ² to Con A, S-Con A and PHA was found to be macrophage-dependent. Optimal mitogenic responses were obtained when macrophage-depleted T-cell populations were reconstituted with 5% normal peritoneal macro-phages. Studies were carried out to investigate the effect of T- and B-cell mitogens on in vitro physical interactions between murine lymphocytes and macrophages. This was done by determining the number of T- or B cells binding to macrophages in the absence and in the presence of T- and B cell mitogens, and comparing the results of these experiments with the induction of lymphocyte proliferation. Con A increased the binding of T cells to macrophages when used in mitogenic doses (1–5 μg/ml). Dose response experiments showed that the same dose of Con A which produced maximal mitogenic stimulation also induced the greatest number of T cells to bind to macrophages. Nonmitogenic doses of Con A (20–50 μg/ml) did not enhance the binding of T cells, while identical doses of S-Con A both induced T cell mitogenesis and increased the number of T cells bound to macrophages. Similar results were obtained with PHA. None of the B-cell mitogens tested (LPS, EPO 127 and LAgl) increased the binding of either T or B cells to macrophages. PWM, which is mitogenic for both T and B cells, increased the binding of T cells to macrophages, but not that of B cells. In brief, the four T-cell mitogens tested (Con A, S-Con A, PHA, and PWM) induced specific physical interactions between T cells and macrophages, while none of the B-cell mitogens had any effect on the physical interactions between either B or T cells and macrophages when used in mitogenic doses.     

Ornithine-containing lipids stimulate CD14-dependent TNF-alpha production from murine macrophage-like J774.1 and RAW 264.7 cells

The ornithine-containing lipids (OL)-induced cytokine production pattern in macrophage-like J774.1 and RAW 264.7 cells was different from that in the peritoneal macrophages previously reported. OLs, as well as lipopolysaccharide (LPS) of Escherichia coli, strongly induced tumor necrosis factor (TNF) alpha but not interleukin (IL)-1beta in J774.1 cells. In the RAW cells, IL-1beta, TNF-alpha and prostaglandin E(2) were strongly induced by the OLs and LPS. OL- and serine-glycine-containing lipid (SGL)-induced TNF-alpha production in J774.1 and RAW 264.7 cells required serum. However, in CD14-deficient LR-9 cells, TNF-alpha was not induced by the OLs in the presence or absence of serum. OLs and a SGL almost completely inhibited the binding of (125)I-LPS to J774.1 cells. These results suggested that OLs and SGL activate macrophages via the CD14-dependent pathway.     

Enhancement of dengue virus infection in cultured mouse macrophages by lipophilic derivatives of muramyl peptides

Dengue virus multiplication in cultures of a murine myelomonocytic cell line (WEHI-3) as well as mouse peritoneal macrophages was enhanced by treatment of the cells with lipophilic derivatives of muramyl peptides for 2 or 3 days before virus inoculation, but not for 2 hr before virus inoculation or during the adsorption period. The infection-enhancing activity of the materials was dependent on their chemical structure, correlating with their immunoadjuvanticity. The infection enhancement in WEHI-3 cells was due primarily to an increase in the number of virus-infected cells which was accompanied by an increased cellular capacity to bind latex particles to their cell surfaces.     

Components of mycobacteria and muramyl dipeptide with adjuvant activity induce lymphocyte activating factor

Several components of mycobacteria including a water-soluble extract (WSA) and an interphase material (IPM) as well as the synthetic cell wall analog muramyl dipeptide (MDP) all stimulated human mononuclear cells (MNL) to produce a factor which was mitogenic for murine thymocytes. The mediator induced by MDP is probably lymphocyte-activating factor (LAF) because it was produced by adherent but not nonadherent MNL and yields two characteristic peaks of activity in the 16,000–22,000 and 60,000–70,000 molecular weight range when eluted from Bio-Gel P-100 columns. The 6-O-stearoyl derivative of MDP was an active inducer of MNL LAF production, whereas, the d-alanine analog of MDP was somewhat less potent. Unfractionated as well as adherent, but not nonadherent, mouse peritoneal cells also produced LAF in response to WSA, IPM, and MDP. P388D₁ cell line macrophages, which are completely devoid of lymphocytes, could be stimulated by WSA, IPM, and MDP to produce LAF after prolonged incubation. These adjuvants did not stimulate nonadherent Balb/C or human blood cells to produce a mitogenic factor. However, when the P388D₁ macrophages were stimulated with these adjuvants in the presence of nonadherent murine or human peripheral blood cells, a mitogenic activity was produced in a shorter period of incubation suggesting that activated lymphocytes can facilitate the production of LAF by macrophages.     

Stimulation of tumor necrosis factor-induced human myelogenous leukemic cell differentiation by high molecular weight PSK subfraction

The mouse macrophage-like cell line, J774.1, spontaneously released differentiation-inducing factor(s). When these cells were treated with a protein-bound polysaccharide, PSK, significantly higher amounts of differentiation-inducing activity were accumulated in the culture supernatant. PSK directly stimulated human myelogenous leukemic cell differentiation induced by J774.1 conditioned medium or by tumor necrosis factor. Among four subfractions of PSK, only the highest molecular weight fraction (MW greater than 200 kD) exerted such a stimulating effect.     

Stimulation of macrophage H2O2 release by resident thymocytes: effect of a soluble factor distinct from interferon-gamma

Activated T cells are known to stimulate macrophage oxidative metabolism and antimicrobial activity through release of interferon-gamma (IFN-gamma). In contrast, the role of nonactivated T cells in regulating macrophage effector functions is less well defined. We have previously reported that a low molecular weight soluble factor derived from resident (nonactivated) thymocytes enhances macrophage receptor-mediated phagocytosis. In the present study, we examined the capacity of resident murine thymocytes to stimulate the respiratory burst and microbicidal activity of peritoneal macrophages. Macrophages cultured for 1-2 days with cell-free thymocyte supernatant (TS) released two to three times more H2O2 in response to PMA or opsonized zymosan than did control macrophages. The H2O2-stimulating factor in TS was distinguished from IFN-gamma by its heat stability (100 degrees C, 20 min), approximate MW of 2400 Da (gel filtration high-pressure liquid chromatography), and absence of interferon activity in both antiviral and enzyme-linked immunosorbent assays. TS-treated macrophages, however, did not exhibit a greater capacity to kill or inhibit the intracellular growth of Toxoplasma gondii, indicating that the thymocyte factor did not fully activate macrophage microbicidal mechanisms. These data suggest that thymocytes can increase the respiratory burst capacity of macrophages in the absence of antigen-specific immune responses.     

Thymocyte differentiation activity from the cloned monocyte/macrophage cell line RAW 264.7. Alterations in the expression of immature thymocyte surface antigens

The cloned monocyte/macrophage cell line RAW 264.7 was previously shown to produce thymocyte mitogenic and co-mitogenic activity that eluted from a Sephadex G-75 column not only at approximately 16,000 daltons, the m.w. described for interleukin 1 (IL 1), but also at 30,000 to 40,000 daltons. The studies reported here indicate that the 30,000 to 40,000 dalton molecule has thymic differentiating activity. Thymocytes from A/J mice were fractionated on discontinuous BSA gradients, which yielded populations of cells enriched for immature and mature cells. The cells found at the interface between 35 and 29% BSA (band 1 cells), which are the most immature, were cultured for 48 hr with highly purified IL 1, with the 30,000 to 40,000 dalton form of thymocyte co-mitogenic activity obtained after Sephadex G-75 chromatography and chromatofocusing chromatography, or with media alone. The surface antigens TL-3, H-2Kk, Thy-1.2, Lyt-1, and Lyt-2 were examined by immunofluorescence. It was found that the highly purified 30,000 to 40,000 dalton species of co-mitogenic activity induced a significant increase in the content of surface H-2Kk, a decrease in TL-3, and a very small decrease in Thy-1.2 on the cell surface, whereas IL 1 was not capable of inducing a change in these surface antigens. There was no change in Lyt-1 on the surface of band 1 thymocytes after incubation with either IL 1 or the 30,000 to 40,000 dalton species. The 30,000 to 40,000 dalton species caused a significant decrease in the percentage of cells staining positive for Lyt-2, whereas IL 1 caused a smaller but significant decrease in Lyt-2. These changes in the surface markers TL-3, H-2Kk, and Thy-1.2 are consistent with changes that occur during thymocyte differentiation. It was also observed that the proliferative response to the 30,000 to 40,000 dalton form and IL 1 increased with increasing functional maturity of each band of thymocytes when used in the thymocyte mitogenic assay. However, only the 30,000 to 40,000 dalton form was capable of inducing a proliferative response in the immature band 1 thymocytes in the thymocyte co-mitogenic assay. These results indicate that the RAW 264.7 cells produce a factor that has, in addition to thymocyte co-mitogenic activity, thymocyte differentiation activity, and this factor is distinct from IL 1.     

Interleukin 1 and prostaglandin production by cells of the mononuclear phagocyte system isolated from mycobacterial granulomas

A study has been made of the activity of interleukin 1 (IL-1) and prostaglandins (PGs) in the culture supernatants from unstimulated and lipopolysaccharide (LPS)-stimulated mycobacteria-induced granuloma cells. Both epithelioid cells from bacillus Calmette-Guerin (BCG)-induced granulomas and macrophages from Mycobacterium leprae-induced granulomas, separated on a fluorescence-activated cell sorter using monoclonal antibody specific to guinea pig macrophages, spontaneously secreted low levels of IL-1 (assayed by thymocyte comitogenic and fibroblast mitogenic activities) into culture supernatants. However, culture supernatants from LPS-stimulated epithelioid cells showed significantly higher IL-1 activity than those from unstimulated cells. In contrast, LPS stimulation of M. leprae granuloma macrophages failed to enhance IL-1 production. Nevertheless, IL-1 activity in the culture supernatants from stimulated mycobacterial granuloma cells of both types was much lower than that from LPS-stimulated peritoneal exudate macrophage culture supernatants. There was no detectable amount of prostaglandin E2 (PGE2) in the culture supernatants from both unstimulated and LPS-stimulated BCG- and M. leprae-induced granuloma cells in comparison to much higher levels of PGE2 produced by unstimulated (0.28-6.2 ng/ml) or LPS-stimulated (greater than 15 ng/ml) peritoneal exudate macrophages. However, BCG granuloma cells either secreted prostaglandin F2 alpha (PGF2 alpha) spontaneously or produced comparable levels of PGF2 alpha to those from peritoneal exudate macrophages on stimulation, while M. leprae granuloma macrophages produced much lower levels of PGF2 alpha.