Suppression of C3H/HeJ cell activation by lipopolysaccharide endotoxin.

Earlier studies in our laboratory showed that the lipopolysaccharide (LPS) of Salmonella typhi, which fails to activate B lymphocytes of C3H/HeJ mice, can suppress proliferation and polyclonal antibody synthesis by these cells when they are stimulated by polyclonal activators. In order to determine what stage of the cell cycle was blocked, resting B cells from C3H/HeJ spleens were activated by using different mitogens in the presence of inhibitory concentrations of LPS and analyzed by flow cytometry, using acridine orange to stain DNA and RNA. LPS was found to inhibit the progression of cells into the G1 stage of the cell cycle. Furthermore, [3H]uridine uptake studies showed that RNA synthesis is inhibited during the early phase of activation. These results indicate that inhibition by LPS of the signalling process occurs during a critical period of the cell cycle when the cells become susceptible to the inhibitory effects of LPS. To examine whether LPS acts only on B cells or whether it can suppress other immunocompetent cells from C3H/HeJ mice, studies were carried out on activated thymocytes and macrophages. LPS was found to inhibit thymocyte proliferation stimulated by concanavalin A or the combination of phorbol myristate acetate and ionomycin. Prostaglandin E2 synthesis by macrophages was also blocked by LPS. Thus, LPS is a potent inhibitor of the functioning of the major immunocompetent cells of C3H/HeJ mice.     

Immune and mitogenic responses by BALB/c, C3H/HeJ, and nude mice to Brucella abortus bacterin and lipopolysaccharide.

The immunogenic and mitogenic properties of Brucella abortus 1119-3 bacterin (BA) and biologically active B. abortus lipopolysaccharide (BA-LPS) were studied using normal and athymic (nude) BALB/c and C3H/HeJ mice. Although BA stimulated 2-mercaptoethanol-sensitive (2-ME-S) primary and secondary antibody responses in all mice, nude mice, in contrast to normal BALB/c and C3H/HeJ mice, did not make substantial 2-mercaptoethanol-resistant (2-ME-R) antibody responses. Similarly, all mice injected with BA-LPS made 2-ME-S primary responses, and the secondary response of thymus-bearing mice contained a substantial 2-ME-R component. Collectively, these observations suggest that although both BA and BA-LPS can stimulate thymus-independent 2-ME-S antibody synthesis, thymus-derived cells are required for optimal immune responses containing a 2-ME-R component. The antibody responses of normal BALB/c and C3H/HeJ mice to BA and BA-LPS were qualitatively and quantitatively similar. Both BA and BA-LPS were mitogenic for spleen cells from normal and nude BALB/c and C3H/HeJ mice but not for thymus cells from normal BALB/c or C3H/HeJ mice, suggesting that both preparations are B-cell mitogens.     

Inhibition of activated nonresponder C3H/HeJ lymphocytes by lipopolysaccharide endotoxin.

The B lymphocytes and macrophages of lipopolysaccharide (LPS) nonresponder C3H/HeJ mice were found to respond to certain R types of LPS endotoxin in a fashion resembling that ordinarily seen with the cells from normal responder mice. DNA synthesis, polyclonal antibody synthesis, and interleukin-1 activity were stimulated by Bordetella pertussis LPS and Salmonella minnesota R595 LPS, although to a lesser extent than with responder cells. Mitogenesis stimulated by both LPSs was inhibited by polymyxin B; this finding provided evidence that any trace endotoxin-associated proteins were not responsible for the activity. Of particular interest was the finding that wild-type smooth LPS actually inhibited activation of the C3H/HeJ B cells not only by the LPS but also by mitogenic proteins, including purified protein derivative of tuberculin. The nonspecific nature of this inhibition and the fact that maximal inhibition occurred some 9 to 12 h into the culture period suggested that the proliferation of the B cells was affected by smooth-type LPS in a manner heretofore unrecognized. These findings permit a new approach to the study of how LPS endotoxin affects cells of the immune system.     

Immunomodulation of the antibody response to lipopolysaccharide in C3H/HeJ mice by complexing with heterologous ribosomes.

We show that formaldehyde fixation of Salmonella typhimurium lipopolysaccharide (LPS) to ribosomes purified from Brucella abortus induced a primary immunoglobulin M (IgM) response to LPS in C3H/HeJ mice and upon revaccination resulted in elevated titers of IgM and induction of IgG antibody to the O antigens of LPS, as measured by an enzyme-linked immunosorbent assay. A similar LPS-Aspergillus fumigatus ribosomal complex yielded IgM and IgG antibody to LPS only after secondary stimulation. These results demonstrate that the hyporesponsiveness of C3H/HeJ mice with respect to antibody formation to LPS can be overcome by complexing this molecule to ribosomal particles and provide a theoretical mechanism for the action of some "ribosomal" vaccines. The results are compatible with the hypothesis that LPS in complex with the ribosomes is converted to a T-dependent form of the antigen to which the C3H/HeJ mice can respond.     

Influence of lipopolysaccharide on graft versus host reactivity of lipopolysaccharide-unresponsive C3H/HeJ mice.

It was initially reported that lipopolysaccharide (LPS)-unresponsive C3H/HeJ mice are refractory to LPS at the B-lymphocyte level, but more recently it has been shown that other cells are similarly unaffected. The current study was undertaken to study an in vivo LPS-modulated disease process involving macrophage-T cell interactions. Adult CBA/J and C3H/HeJ mice were used as spleen donors, and graft versus host reactions were induced in BALB/c neonates. Prior LPS treatment of CBA/J adults decreased the ability of their spleen cells to cause fatal graft versus host disease in BALB/c neonates, whereas no difference was found between injection of spleen cells from normal or LPS-treated C3H/HeJ mice. Similar results were obtained with these cell types when the mouse spleen mixed leukocyte culture system was used. In a carbon clearance assay for stimulation of the reticuloendothelial system with LPS, it was found that the rate of phagocytosis was significantly increased in BALB/c and CBA/J mice 72 h after inoculation of LPS. No stimulation was seen in rate of carbon uptake in the C3H/HeJ animals after treatment with phenol-extracted LPS or with butanol-extracted LPS. An LPS-induced protective serum factor was produced only in the LPS-responsive CBA/J mice and was specific for the syngeneic cells.     

Adjuvant actions of linear mannan-possessing lipopolysaccharide (LPS) in LPS-resistant C3H/HeJ mice.

Immunopotentiation has been demonstrated when Klebsiella O3 lipopolysaccharide (KO3 LPS), which possesses a linear mannan as the O-specific side chain, was injected subcutaneously into endotoxin resistant C3H/HeJ mice together with soluble protein antigens. The LPS exhibited significantly positive adjuvant effects on antibody responses in vivo after secondary antigen challenge and on delayed-type hypersensitivity (DTH) reactions against protein antigens. However, KO3 LPS was not a polyclonal B cell activator (PBA) in C3H/HeJ mice nor mitogenic in cultures of spleen cells of C3H/HeJ. Thus, the activity of the LPS in C3H/HeJ mice is confined to the potentiation of T-dependent immune responses. The contribution of the mannan O side chain to the adjuvant action of KO3 LPS was suggested.     

Analysis of the effects of lipopolysaccharide on macrophages: differential phagocytic responses of C3H/HeN and C3H/HeJ macrophages in vitro.

The phenomenon of lipopolysaccharide (LPS)-induced in vitro macrophage cytotoxicity has been reported by a number of investigators but has often been difficult to reproduce and to quantitate. In this report, we have examined the effect of LPS on the ability of macrophages to ingest 51Cr-labeled, opsonized sheep erythrocytes as a method for examining the direct toxic effects of LPS on macrophages in vitro. By using this assy, we can clearly discriminate between LPS responder C3H/HeN macrophages and LPS nonresponder C3H/HeJ macrophages and demonstrate that LPS induces a profound inhibition of Fc-mediated phagocytosis in LPS responsive macrophages. Furthermore, low concentrations of LPS stimulate phagocytosis in macrophages derived for C3H/HeJ mice. The lipid A moiety of the LPS is responsible for the observed enhancement or inhibition of Fc-mediated phagocytosis. This assay was more sensitive than LPS-induced cytotoxicity, since inhibition of phagocytosis was detectable in cultures of LPS-sensitive macrophages even when cytotoxicity, assessed by trypan blue exclusion, was not. Thus, this assay represents an extremely sensitive method for analyzing the direct effects of LPS on macrophages.     

Glycolipid induced proliferation of lipopolysaccharide hyporesponsive C3H/HeJ splenocytes

Although the C3H/HeJ mouse is hyporesponsive to lipopolysaccharides (LPS), certain forms of the lipid A fraction have been shown to stimulate cells from this mouse strain. To determine the role of the oligosaccharide chain length on the lipid A-induced proliferation of C3H/HeJ splenocytes, a panel of glycolipids from R-chemotypes (Re, Rc, and Rd) and a nontoxic monophosphoryl lipid A (MPL) were tested. The MPL cells isolated from the MPL of Salmonella minnesota, Salmonella typhimurium, and the Reglycolipids isolated from Escherichia coli were found to be effective at stimulating the LPS-hyporesponsive spleen cells. A Re-glycolipid isolated from a different strain of E. coli cells was inactive, as were the S. minnesota Rc and Rd chemotypes. Proliferation induced by MPL and the active Re preparations was dose dependent and was inhibited by polymyxin B. Thus, if contamination of the Re-LPS or MPL with lipid A-associated protein occurred, it was below functional levels. The data suggest that the C3H/HeJ spleen cells are capable of responding to certain glycolipids, but they may lack the ability to convert native LPS into a stimulatory signal. In addition, a monosaccharide precursor of lipid A (lipid X), and a monoacyl glucosamine phospholipid derivative of lipid X (MaGP), were capable of inhibiting the proliferation induced by the MPL and Re-glycolipids. These data are compatible with the existence of a spleen cell receptor for lipid A.     

Failure of bacterial lipopolysaccharide to elicit a cytostatic effect on Plasmodium vinckei petteri in C3H/HeJ mice.

Malarial parasites, Plasmodium vinckei petteri, taken from lipopolysaccharide (LPS) high-responder (C3H/HeJGiFWeHi) mice which had been injected 7 to 8 h previously with either Escherichia coli LPS B or LPS W incorporated the purine nucleotide precursor hypoxanthine more slowly in an in vitro assay than parasites taken from saline-injected controls. In contrast, malarial parasites taken from LPS low-responder C3H/HeJ mice after injection of either LPS B or LPS W did not show reduced levels of hypoxanthine incorporation. These differing results with LPS high- and low-responder mouse strains demonstrated that the cytostatic effect on the parasites seen in the high-responder strain was not due to the direct action of LPS and implied that the cytostasis was mediated via host lymphoreticular cells. Furthermore, the failure of LPS B, a lipid A-associated protein-containing LPS preparation, to elicit a cytostatic effect on P. vinckei petteri in C3H/HeJ mice suggested that the LPS-induced effector mechanisms acting against malarial parasites may be similar to those reported against bacteria and tumors.     

Resistance of C3H/HeJ mice to the effects of Haemophilus pleuropneumoniae.

Comparisons were made in the mortality associated with an inhaled dose of viable Haemophilus pleuropneumoniae type 5, strain J45, between adult C3H/HeN and C3H/HeJ mice. Mice of both strains were also challenged with Escherichia coli strains O111:B4 and J5. The 50% lethal dose (LD50) of H. pleuropneumoniae in C3H/HeN mice was calculated to be 10(6.5) CFU. At a mean dose of 10(6.7) CFU a 46% mortality rate occurred in C3H/HeN mice, whereas only 10% of the C3H/HeJ mice died (P less than 0.01). Deaths occurred significantly earlier in C3H/HeN mice (P less than 0.01). No deaths occurred later than 12 h postinfection in either group. Pulmonary lesions in the mice that died were similar to those in pigs that die during the acute phase of H. pleuropneumoniae infection. In surviving mice of both strains, a mild resolving interstitial and bronchopneumonia was present which was not typical of subacute H. pleuropneumoniae infections in swine. Quantitative bacterial isolations from the lungs, liver, and spleen indicate that H. pleuropneumoniae did not multiply in the lungs, was rapidly cleared, and did not become systemic. No deaths occurred in the mice inoculated with E. coli J5 or O111:B4 at mean doses of 10(6.3), 10(7.2), and 10(8.5) CFU, and 10(6.4), 10(7.5), and 10(8.2) CFU, respectively. The difference in the mortality rate between the C3H/HeN and C3H/HeJ mice suggests that endotoxin may be involved in acute deaths in pigs infected with H. pleuropneumonia. As indicated by the E. coli challenge, however, other factors are also likely to be involved. Because of the differences in the pathology and microbiology following H. pleuropneumoniae pulmonary infections in mice and pigs, mice do not appear to be an accurate model of the overall disease in swine.     

Immunomodulatory activity of monophosphoryl lipid A in C3H/HeJ and C3H/HeSnJ mice.

Treatment with nontoxic monophosphoryl lipid A (MPL) derived from a polysaccharide-deficient, heptoseless Re mutant of either Salmonella typhimurium or Salmonella minnesota R595 enhanced the immunoglobulin M (IgM) anti-type III pneumococcal polysaccharide (SSS-III) antibody response of C3H/HeSnJ mice. Such an adjuvant effect was not observed in lipopolysaccharide-nonresponder C3H/HeJ mice. Nevertheless, C3H/HeJ spleen cells produced a weak mitogenic response to both preparations of MPL in vitro, and C3H/HeJ mice showed a significant increase in serum IgM levels without an increase in numbers of splenic IgM-secreting plaque-forming cells after in vivo treatment with MPL. A significant increase in serum IgG3 levels was accompanied by a transient decrease in serum IgG1 levels in C3H/HeSnJ mice given MPL; such non-antigen-specific polyclonal effects were not observed in C3H/HeJ or in athymic nu/nu mice. Since the enhanced antibody response to SSS-III has been attributed to the inactivation of suppressor T cells by MPL and since suppressor-T-cell activity is demonstrable in both C3H/HeSnJ and C3H/HeJ mice, these findings imply that (i) the suppressor T cells of C3H/HeJ mice are refractory to inactivation by MPL and (ii) some of the polyclonal and mitogenic effects produced in C3H/HeJ mice are due to the direct action of MPL on B lymphocytes.     

Induction of auto-antibody formation in C3H/HeJ mice by cobra venom factor.

Recently, we demonstrated that lipopolysaccharide (LPS)-hyporesponsive C3H/HeJ mice show a very high background number of splenic antibody-forming cells with specificity for bromelain-treated isologous erythrocytes. This background level was not or only slightly enhanced by LPS injection. In this paper it is reported that the existing response of C3H/HeJ mice is about doubled by treatment of the animals with cobra venom factor (CVF). This increase is very similar to the LPS-induced potentiation of the auto-antibody response of C3H/Tif and other LPS-responder mice. The absence of auto-antibodies in the sera of CVF-treated C3H/HeJ mice, however, points at a different mechanism of B cell activation. The mediation of the CVF-induced stimulation of the B cells of C3H/HeJ mice by covalent C3-glycoprotein complexes and the need for an additional stimulus is discussed.     

Altered B-lymphocyte membrane architecture indicated by ganglioside accessibility in C3H/HeJ mice.

We have analyzed both the total ganglioside composition and the surface accessibility of C3H/HeN B lymphocytes and C3H/HeJ B lymphocytes. Seventeen individual resorcinol-positive moieties were visualized by two-dimensional thin-layer chromatography of the purified gangliosides from both strains. Complete homology between strains was seen in the patterns of total gangliosides purified from the endotoxin-responsive and -hyporesponsive strains, with only minor differences in the relative concentrations of four gangliosides. In comparison, only 12 individual gangliosides were accessible to surface labeling following galactose oxidase treatment in these same strains, suggesting that some gangliosides are masked at the cell surface in both strains. However, labeling of the more polar components was greatly reduced in the endotoxin-hyporesponsive (C3H/HeJ) strain, suggesting that these gangliosides have decreased accessibility to galactose oxidase at the cell surface. Therefore, while the total ganglioside compositions of the two strains were nearly equivalent, there were dramatic differences in ganglioside surface accessibility. These findings indicate that an alteration in membrane structure that is associated with the endotoxin hyporesponsiveness observed in C3H/HeJ B lymphocytes exists.     

Difference in susceptibility to gram-negative urinary tract infection between C3H/HeJ and C3H/HeN mice

The difference in susceptibility to urinary tract infection between C3H/HeJ and C3H/HeN mice was tested for with gram-negative strains differing in lipopolysaccharide composition. Recently, impaired clearance of Escherichia coli from the kidney of C3H/HeJ compared to C3H/HeN mice was shown to be correlated with the LPS low responsiveness. In this study, a difference in clearance from the kidneys of C3H/HeJ and C3H/HeN mice was found only with lipopolysaccharide-containing bacteria. Gram-positive bacteria, e.g., Staphylococcus saprophyticus and Streptococcus agalactiae, were recovered in essentially equal numbers from the kidneys of mice of both strains. In contrast, of the lipopolysaccharide-containing strains used, all persisted in higher numbers in the kidneys of C3H/HeJ mice than in the kidneys of C3H/HeN mice. Variations in the O side chain did not eliminate this difference. E. coli Hu734 O75+K5+ and the rfb- mutant O75-K5+ remained in similar numbers in C3H/HeJ mice, although O75-K5+ was eliminated more rapidly in C3H/HeN mice. The core structure did not affect the differential persistence in the two mouse strains. The rfb mutants with R1-R4 cores were eliminated after 24 h from the C3H/HeN mice, but remained in significant numbers in the kidneys of C3H/HeJ mice. Even the Re mutant of Salmonella minnesota persisted in low numbers in C3H/HeJ mice. The relative bacterial recovery from either mouse strain was related to the overall virulence of the infecting bacterial strain, but the difference between C3H/HeJ and C3H/HeN mice was associated with responsiveness to parts of lipopolysaccharide common to the bacterial strains tested.     

Functional role of interleukin 1 in periodontal disease: induction of interleukin 1 production by Bacteroides gingivalis lipopolysaccharide in peritoneal macrophages from C3H/HeN and C3H/HeJ mice.

Hot phenol-water-extracted lipopolysaccharide (LPS) from Bacteroides gingivalis 381 was purified by Sephadex G-100 chromatography with Tris buffer supplemented with sodium deoxycholate and EDTA (B-LPS). In the present study, B-LPS was examined for its ability to induce interleukin 1 (IL-1) production, a mitogenic response, and macrophage activation in LPS high-responder C3H/HeN and low-responder C3H/HeJ mice. A significant increase in IL-1 production was observed in C3H/HeN and C3H/HeJ peritoneal macrophages treated with various doses (1.0 to 50 micrograms/ml) of B-LPS. IL-1 production by C3H/HeN macrophages treated with B-LPS (10 micrograms/ml) was about seven times greater than that by C3H/HeJ macrophages. However, the IL-1 production induced by B-LPS (10 micrograms/ml) in C3H/HeN macrophages was four times lower compared with that induced by Escherichia coli O111 B4 LPS. Also, a significant increase in IL-1 production was found in human monocytes stimulated with B-LPS. That B-LPS-induced IL-1 exhibits some molecular weight heterogeneity was indicated from Sephadex G-75 gel filtration profiles. A significant, high mitogenic response by whole spleen cells with 1 X 10(5) to 5 X 10(4) cells of either mouse strain per well treated with B-LPS (10 to 50 micrograms/ml) was observed. However, the response of C3H/HeJ mice was less than that of the C3H/HeN strain. Also, glucose consumption assays indicated that enhanced macrophage activation occurred in C3H/HeN but not in C3H/HeJ mice treated with B-LPS. In light of recent studies showing that IL-1 stimulates bone resorption in a mouse calvaria system and collagenase production in fibroblasts, we suggest that B-LPS-induced IL-1 may play a significant role in the pathogenesis of adult periodontal disease.     

Induction of syngeneic graft-versus-host disease in LPS hyporesponsive C3H/HeJ mice.

Syngeneic GVHD (SGVHD) develops following syngeneic bone marrow transplantation and treatment with cyclosporine A. Previous studies have demonstrated a role for IL-12, IFN-gamma, and TNF-alpha in the development of murine SGVHD. Macrophages can be activated to secrete IL-12 and TNF-alpha via a T-cell-dependent or T-cell-independent pathway (LPS or bacterial products). Studies were designed to determine if LPS participated in the development of SGVHD in C3H/HeN (LPS-responsive) and C3H/HeJ (LPS-hyporesponsive) mice. C3H/HeJ and C3H/HeN mice had similar levels of disease induction and pathology. Following induction of SGVHD, treatment of C3H/HeN, but not C3H/HeJ, mice with a sublethal dose of LPS resulted in mortality. However, neutralization of IL-12 abrogated the development of disease in C3H/HeJ mice, demonstrating that activated macrophages and their products participated in the development of SGVHD in these animals. These data suggested that LPS responsiveness was not a predisposing factor for SGVHD induction.     

Experimental Pneumocystis carinii pneumonia in C3H/HeJ and C3HeB/FeJ mice

C3H mice develop heavier degrees of Pneumocystis carinii pneumonia than other mouse strains tested. We have compared P. carinii pneumonia in two strains of C3H mice: C3H/HeJ mice, which are unresponsive to the effects of bacterial lipopolysaccharide (LPS), have defects in macrophage function, and have increased antibody responses to orally administered T-dependent antigens; and C3HeB/FeJ mice, which are immunologically normal. P. carinii pneumonia was induced by corticosteroids, and the intensity of the infection was judged by a semiquantitative histopathologic scoring system. Heavier degrees of infection were found in C3H/HeJ mice than in C3HeB/FeJ mice. Serum antibodies to P. carinii, measured by an indirect fluorescent antibody technique, were mainly of the IgG class in both strains of mice and varied inversely with the intensity of P. carinii infection in the lungs. Antibody levels were significantly higher in C3H/HeJ mice than in C3HeB/FeJ mice. These data suggest that C3H/HeJ have increased susceptibility to the effects of steroids of host defenses against P. carinii, and heightened serum antibody responses to the organism.     

The surface phenotypic characterization of lung macrophages in C3H/HeJ mice.

We have investigated the surface phenotypic profile of murine lung macrophages in frozen tissue sections, in single-cell suspensions obtained by endobronchial lavage, and in collagenase digests of parenchymal lung tissue, using a panel of monoclonal antibodies directed against pan macrophage markers and antigens present on distinct lymphoid-associated macrophage subpopulations. Our results indicate that lung macrophages from specific pathogen-free (SPF), lipopolysaccharide (LPS) hyporesponsive C3H/HeJ mice are relatively homogeneous no matter what lung tissue compartment they are obtained from. Their predominant surface phenotype was F4/80weak, M1/70-, MOMA-2+, NLDC-145+, MOMA-1+, SER-4+, which resembles the pattern of expression by lymphoid macrophages rather than representative tissue macrophages such as those found in the peritoneal cavity. These results are consistent with the current paradigm that lung macrophages, like lymphoid macrophages, play an important immunoregulatory role within their microenvironment.     

Comparison of thymocyte and T lymphocyte gangliosides from C3H/HeN and C3H/HeJ mice

Gangliosides have been prepared from resting murine thymocytes and splenic T cells. Profoundly different two-dimensional thin layer chromatography (2D TLC) patterns were observed between these two cell types. Thymocytes contained 28-30 discrete gangliosides of which eight represented major gangliosides. Splenic T lymphocytes from both strains had much simpler patterns, with six to seven major gangliosides and 12-13 minor gangliosides. Computerized analysis of the thymocyte ganglioside patterns between LPS-responder C3H/HeN mice and lipopolysaccharide (LPS)-hyporesponsive C3H/HeJ mice revealed no significant difference in the major gangliosides. However, with splenic T cell gangliosides, there is a striking difference in the relative proportion of three homologous gangliosides between the two strains. Consistent with previous observations on macrophage gangliosides, the ratio of N-acetylneuraminic acid-containing ganglioside to N-glycolylneuraminic acid-containing ganglioside was higher in both thymocytes and T-cells from the LPS-responder strain. These results show that sialic acid-containing glycolipids from thymocytes and T lymphocytes between endotoxin responder and hyporesponder strains manifest small but significant changes. These differences are present in unstimulated cell populations and may represent a manifestation of the Lps gene.     

Comparative effects of particulate and soluble glucan on macrophages of C3H/HeN and C3H/HeJ mice.

In order to compare both the actions of soluble glucan (glucan-F) and particulate glucan (glucan-P) on macrophages and the responsiveness of macrophages from C3H/HeJ and C3H/HeN mice to these immunomodulators, interleukin-1 (IL-1) levels, phagocytosis and superoxide production were monitored after an in vitro exposure to glucan-F or glucan-P. A 2 or 20 h exposure to either glucan preparation decreased the ability of both C3H/HeJ and C3H/HeN macrophages to ingest zymosan. In contrast, glucan-P, but not glucan-F, decreased (after a 20 h exposure) the uptake of both IgG opsonized erythrocytes and latex beads. Furthermore, glucan-P, but not glucan-F was as effective as zymosan (after a 1 h exposure) in inducing superoxide release by macrophages isolated from both C3H/HeN and C3H/HeJ mice. While the effects of glucan-P on PMA-induced superoxide release and IL-1 levels were similar in macrophages from C3H/HeJ and C3H/HeN mice, glucan-F was ineffective at enhancing PMA-induced superoxide release or increasing IL-1 levels in C3H/HeJ mice. Thus (1) the effects of glucan-P on phagocytosis of opsonized erythrocytes and latex beads are not mimicked by glucan-F and (2) while macrophages from C3H/HeJ mice respond normally (as compared with C3H/HeN macrophages) to glucan-P, they are hyporesponders to glucan-F. These findings indicate that the activation of macrophages by glucan-P involves different (or additional) pathways from those activated by glucan-F.