Macrophage-stimulating effect of a synthetic muramyl dipeptide and its adjuvant-active and -inactive analogs for the production of T-cell activating monokines

Immunologic effects of yogurt

Many investigators have studied the therapeutic and preventive effects of yogurt and lactic acid bacteria, which are commonly used in yogurt production, on diseases such as cancer, infection, gastrointestinal disorders, and asthma. Because the immune system is an important contributor to all of these diseases, an immunostimulatory effect of yogurt has been proposed and investigated by using mainly animal models and, occasionally, human subjects. Although the results of these studies, in general, support the notion that yogurt has immunostimulatory effects, problems with study design, lack of appropriate controls, inappropriate route of administration, sole use of in vitro indicators of the immune response, and short duration of most of the studies limit the interpretation of the results and the conclusions drawn from them. Nevertheless, these studies in toto provide a strong rationale for the hypothesis that increased yogurt consumption, particularly in immunocompromised populations such as the elderly, may enhance the immune response, which would in turn increase resistance to immune-related diseases. This hypothesis, however, needs to be substantiated by well-designed randomized, double-blind, placebo-controlled human studies of an adequate duration in which several in vivo and in vitro indexes of peripheral and gut-associated immune response are tested.

In vitro TNF-alpha production and in vivo alteration of TNF-alpha RNA in mouse peritoneal macrophages after treatment with different bacterial derived agents

Since muramyl dipeptide (MDP) was recognized as a potent monocyte/macrophage activating agent, many MDP analogues were synthesized and tested for their ability to augment the host immune defence system against neoplasms. This study was performed to determine whether the newly synthesized desmuramyl N-acyl dipeptides LK 409 and LK 410 were also capable of affecting the immune system. For this purpose, the peritoneal macrophages were incubated in vitro with these two agents and TNF-alpha production was measured. In addition, the effect of LK 409 and LK 410 on TNF-alpha and IL-1 RNA levels in in vivo stimulated macrophages was determined by quantitative polymerase chain reaction (RT-PCR). None of the LK 409 and LK 410 concentrations tested were able to render macrophages in vitro to excrete a detectable amount of TNF-alpha in the supernatant fluid. However, the TNF-alpha and IL-1 RNA levels in macrophages of in vivo treated mice (C57Bl/6) were increased in comparison to mock-treated mice. The results indicate that LK 409 and LK 410 are capable of inducing an increase in TNF-alpha and IL-1 RNA levels, yet in vitro TNF-alpha production remains under detectable levels (40 U/ml).

Catabolic effects of muramyl dipeptide on rabbit chondrocytes

Muramyl dipeptide, an essential structure for the diverse biologic activities of bacterial cell wall peptidoglycan, inhibited the synthesis of glycosaminoglycan/proteoglycan in cultured rabbit costal chondrocytes in a dose-dependent manner. Muramyl dipeptide, as well as lipopolysaccharide and interleukin-1 alpha, also enhanced the release of 35S-sulfate-prelabeled glycosaminoglycan/proteoglycan from the cell layer, which seems to reflect, at least partially, the increasing degradation of glycosaminoglycan/proteoglycan. Five synthetic analogs of muramyl dipeptide known to be adjuvant active or adjuvant inactive were tested for their potential to inhibit synthesis of glycosaminoglycan/proteoglycan and to enhance the release of glycosaminoglycan/proteoglycan in chondrocytes. The structural dependence of these synthetic analogs on chondrocytes was found to parallel that of immunoadjuvant activity. These results suggest that muramyl dipeptide is a potent mediator of catabolism in chondrocytes.

Induction, in vivo and in vitro, of macrophage membrane interleukin-1 by adjuvant-active synthetic muramyl peptides

Recent evidence has shown that a membrane form of interleukin-1 (IL-1) serves as a necessary signal for antigen presentation, leading to T-cell activation. The synthetic immunostimulant muramyl dipeptide (MDP) is known to induce secretion of IL-1 and its adjuvant effect was found to be mediated through enhancement of T-helper cells. We have investigated the ability of MDP and 19 other adjuvant-active or -inactive MDP analogs and derivatives to induce membrane IL-1 in mouse peritoneal macrophages. Enhancement in vitro of membrane expression and secretion of IL-1 in fresh or aged cultures of macrophages was observed after stimulation with MDP or with adjuvant-active but not with adjuvant-inactive muramyl peptides. Administration in vivo of adjuvant-active doses of MDP or of any of 12 other active analogs induced high levels of macrophage membrane IL-1 detected by the lymphocyte-activating factor assay. This effect was not observed when 7 other adjuvant-inactive derivatives were used. Moreover, under conditions where MDP did not exert an adjuvant effect, this immunomodulator was found to be incapable of inducing the expression of macrophage membrane IL-1. These results demonstrate a very high correlation between the ability to induce membrane IL-1 and the adjuvant activity of muramyl peptides. The correlation was observed irrespective of other biological effects of the synthetic adjuvants such as pyrogenicity and/or anti-infectious activity.

Anti-infectious activity of liposomal muramyl dipeptides in immunodeficient CBA/N mice

Two muramyl dipeptides, N-acetylmuramyl-L-alanyl-D-isoglutamine and its adjuvant-inactive isomer N-acetylmuramyl-D-alanyl-D-isoglutamine, were examined for their ability to protect mice carrying the CBA/N immune deficiency gene (xid) against lethal bacterial challenge. Prophylactic treatment with N-acetylmuramyl-L-alanyl-d-isoglutamine gave significant protection against Streptococcus pneumoniae, Salmonella typhimurium, and Salmonella enteritidis infection. N-Acetylmuramyl-D-alanyl-D-isoglutamine was unable to confer protection. Incorporation of the lipophilic glycerol dipalmitate derivatives of the two muramyl dipeptides within liposomal carriers resulted in a significant enhancement of anti-infectious activity, both with respect to number of survivors and length of survival. Liposomal muramyl dipeptides were 10- to 15-fold more potent than free muramyl dipeptide; enhanced potency was most evident with N-acetylmuramyl-D-alanyl-D-isoglutamine. Prophylactic treatment with liposomes containing the lipophilic muramyl dipeptides resulted in enhanced clearance of bacteria from the blood (greater than 3-fold increase in rate) when compared with that of hydrosoluble N-acetylmuramyl-L-alanyl-D-isoglutamine, indicating a correlation between reticuloendothelial stimulation and anti-infectious activity.

Muramyl dipeptide induced augmentation of the proliferative response of thymocytes to phytohemagglutinin

N-Acetylmuramyl-L-alanyl-D-isoglutamine (MDP) augmented the proliferative response of thymocytes to phytohemagglutinin (PHA). The augmenting effect of MDP disappeared by passage of glass-nonadherent thymocytes through Sephadex G-10 (G-10) column or by removal of low density cells by the Ficoll-Conray gradient centrifugation. The diminished augmenting effects of MDP on the proliferative response of glass-nonadherent-G-10 nonadherent thymocytes was restored by the addition of the G-10 adherent cells. When G-10 adherent cell fraction was extensively depleted of macrophages by glass adherence and EA-rosetting, it was found that neither the macrophage-depleted G-10 adherent cell fraction nor the macrophage fraction supported by itself the proliferative response of G-10 nonadherent thymocytes. However, addition of macrophage fraction together with the macrophage-depleted G-10 adherent cells did support the proliferation of G-10 nonadherent thymocytes. It was further shown that peritoneal exudate macrophages could be substituted for thymic macrophage fraction. These results suggested that both the G-10 adherent-glass nonadherent cells and macrophages were essential for the MDP-induced augmentation of the proliferative response of thymocytes to PHA and these cells exerted different accessory roles in this response.

Augmentation of human blood monocyte microbicidal activity by RU 41740, a glycoprotein extract from Klebsiella pneumoniae

Non-specific activation of host defences may have a significant impact on the outcome of infections in the immunocompromized patient. RU 41740, a glycoprotein extract from Klebsiella pneumoniae, effective in increasing resistance to experimental infections in animals, has been examined in vitro for its effect on human blood monocyte locomotion, phagocytosis, killing of Candida albicans, and release of superoxide anion. RU 41740 had no chemo-attractant activity nor any effect on monocyte chemotactic and phagocytic function. Candidacidal capacity and superoxide anion production by monocytes were significantly enhanced after preincubation with RU 41740 greater than 1.0 microgram/ml. The effect was dose- and time-dependent and was not influenced by the presence of lymphocytes or their culture supernatants. This suggests a direct interaction with monocytes as the mechanism of action of the extract.

Stimulatory effects of muramyl dipeptide and its butyl ester derivative on the proliferation and activation of macrophages in vitro

Muramyl dipeptide (MDP) and the butyl ester derivative, N-acetylmuramyl-L-alanyl-D-glutamine-alpha-n-butyl ester (MDP[Gln]OnBu), were shown to induce the in vitro proliferation of oil-induced guinea pig peritoneal exudate cells (PEC). Both agents induced 10-20 fold increases in tritiated thymidine incorporation in PEC cultures. The maximal effects occurred in 72 h cultures stimulated with either 0.1 microgram MDP or 10 micrograms MDP[Gln]OnBu. The mitogenic effects of MDP appeared to be mediated by a macrophage product detected in the supernatants of MDP-stimulated cultures. Supernatants of MDP- or MDP[Gln]OnBu-stimulated PEC cultures were also inhibitory to normal fibroblast growth and cytotoxic to L929 tumor cells. These results indicated that these agents may stimulate macrophages by modulating secretory functions. In addition, either peptidoglycan was capable of activating bactericidal activity in in vitro macrophage cultures. Initial studies of possible mechanisms of action revealed an early increase in the level of cyclic GMP. The possible role of cyclic GMP in mediating the stimulation of macrophage secretory processes is discussed.

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.

Mechanisms in opposite modulation of spleen cell and lymph node cell responses to mitogens following muramyl dipeptide treatment in vivo

It has been reported that a muramyl dipeptide (MDP) treatment regimen (200 micrograms MDP per mouse, Days -4, -3, -2, and -1) that, given prophylactically, affords protection against several infectious agents also induces lymph node hyperplasia, lymph node cell (LNC) hyperresponsiveness to mitogens, and spleen cell hyporesponsiveness to mitogens. The purpose of the present work was to extend those studies and delineate cellular mechanisms involved in these phenomena. It has been found that hyperresponsiveness of LNC was prolonged (7 days) posttreatment; in contrast, hyporesponsiveness of spleen cells was transient and rebounded by Day 4 posttreatment. Hyperresponsiveness of LNC and hyporesponsiveness of spleen cells actively enhanced and depressed normal lymphoid cell responses, respectively, in cell mixing experiments. Hyporesponsiveness of spleen cells was associated with the plastic-nonadherent, non-B-cell fraction and nylon wool-nonadherent subpopulations. Indomethacin (10(-6) M) did not abrogate hyporesponsiveness of spleen cells. These data suggest that splenic suppressor T cells result from MDP treatment and were responsible for spleen cell hyporesponsiveness. On the other hand, hyperresponsiveness of LNC was associated with the nylon wool-adherent cell subpopulations and a higher percentage of nonspecific esterase-positive cells. Hyporesponsiveness of spleen cells was associated with deficient production of interleukin 2 (IL-2), but not of interleukin 1 (IL-1). In contrast, hyperresponsiveness of LNC was not explained by enhanced IL-1 or IL-2 production.

In vitro inhibition of murine B-cell tumor growth by MDP, MDP(D-D) and Vaccin is mediated by macrophages

The effect of two muramyl dipeptides, N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) and N-acetylmuramyl-D-alanyl-D-isoglutamine (MDP(D-D)), on the in vitro growth of two murine ascitic plasmacytomas, MOPC 173 and TEPC 15, and on an ascitic lymphoma cell line, ABPL2, was studied. The ability of the muramyl dipeptides to inhibit tumor cell growth was compared with a sonicated antigenic preparation of Mycobacterium vaccae (Vaccin), known to have macrophage stimulation activity. The growth of all three ascitic cell lines was inhibited by both muramyl dipeptides and Vaccin. Macrophage-depletion of the ascitic cell populations led to an increase in cell growth of TEPC 15 and MOPC 173, and a decrease in ABPL2. A reduction or loss of the inhibitory activity of the muramyl dipeptides or Vaccin was also observed, and no inhibitory activity was found when the tumor cell lines were cultured in vitro to render them macrophage-free. The inhibitory activity of MDP or MDP(D-D) was restored when purified ascitic macrophages were added to the in vitro cultured cell lines. It was demonstrated that a minimum number of macrophages were necessary for the expression of inhibitory activity. Indomethacin, a PG-synthetase inhibitor, was found to act in a synergistic manner with MDP and MDP(D-D) in inhibiting TEPC 15, but antagonized the effect of these two agents on ABPL2. The lymphoma cell line ABPL2 appeared to be the most sensitive to inhibition by MDP(D-D), a nonpyrogenic, adjuvant-inactive stereoisomer of MDP.

Partial characterization of thymocyte-activating factor derived from MDP-stimulated guinea pig fibroblasts

The activity of fibroblast-derived thymocyte activating factor (FTAF) of the guinea pig was measured, and the factor was partially characterized. The FTAF activity was heat labile, and destroyed by treatment with trypsin, chymotrypsin, and Streptomyces griseus protease, suggesting the protein nature of FTAF. FTAF bound to DEAE-Sepharose CL-6B in Tris-HCl buffer at pH 8.0, and was eluted with 0.1-0.2 M NaCl. FTAF was absorbed with Blue Sepharose CL-6B. The factor bound to a hydroxylapatite column in 10 mM phosphate buffer and was eluted in two major fractions, one fraction with 40 mM phosphate buffer, the other with 70-110 mM phosphate buffer. Finally, FTAF did not have as much effect on the proliferation of lymph node T cells as T-cell-activating monokines which exhibited marked stimulating effects on both T lymphocytes and thymocytes.

Augmentation of the proliferative response of thymocytes to phytohemagglutinin by the muramyl dipeptide1

A synthetic N-acetylmuramyl-L-alanyl-D-isoglutamine or muramyl dipeptide (MDP) and adjuvant-active analogs, but not lipopolysaccharide (LPS), exhibited the augmenting effect on the proliferative response of thymocytes to phytohemagglutinin (PHA). MDP also had a comitogenic effect on PHA-stimulated T lymphocytes. It was shown that the thymocyte-stimulating effect of MDP is not through the production of the monikines by MDP-stimulated macrophages and that MDP has a direct action on lymphocytes.

Two adjuvant-active muramyl dipeptide analogs induce differential production of lymphocyte-activating factor and a factor causing distress in guinea pigs

Many adjuvant-active analogs of muramyl dipeptide (MDP) have been described. Unfortunately, most have been found to induce pyrexia or other adverse side effects in several species. In the guinea pig, these side effects include the guinea pig distress syndrome, which lasts 24 to 48 h, and enhancement of endotoxin shock. A dose-related response to MDP or N-acetylmuramyl-L-alpha-aminobutyryl-D-isoglutamine [( Abu1]-MDP) was observed. However, we found several adjuvant-active analogs which were completely innocuous in guinea pigs. 2-(2-Acetamido-2-deoxy-D-glucose-3-O-yl)-D-hexanoyl-L-alanyl-D-isoglutam ine (3'-n-propyl-MDP) was one such compound. To understand the differences between the toxic and nontoxic compounds, macrophage stimulation in vitro was studied. Both compounds stimulated guinea pig peritoneal macrophages to produce lymphocyte-activating factor in vitro. However, the supernatant from 3'-n-propyl-MDP-stimulated macrophages had no observable effects on guinea pigs, whereas the dialyzed supernatant from [Abu1]-MDP-stimulated cells readily induced the guinea pig distress syndrome. Sephadex G-150 chromatography showed that both analogs stimulated production of a major (60,000) and minor (11,000) peak of lymphocyte-activating factor activity. The factor causing the guinea pig distress syndrome was found only in the low-molecular-weight fraction of [Abu1]-MDP-treated cell supernatants. Thus, one difference between the nontoxic and toxic compounds is their ability to produce lymphocyte-activating factor in the absence of the toxic factor. The lack of toxicity of 3'-n-propyl-MDP makes it an attractive compound for use in vaccines.

In vitro spleen cell proliferation following in vivo treatment with a synthetic glycolipid or lipid A in three mouse strains

Synthetic glycolipid, maltose hexastearate (MHS), like LPS or lipid A is a B cell mitogen for outbred Swiss mice, inbred C3H/HeN and C3H/HeJ X C3H/HeN F1 hybrid but not for C3H/HeJ mice. MHS administered i.p. (10 micrograms) to Swiss, C3H/HeN, C3H/HeJ and C3H/HeJ X C3H/HeN F1 hybrid mice confers within 90 min an increased ability in the spleen cell populations such that they exhibit increased incorporation of 3H thymidine into cellular DNA in vitro. The spleen cells of MHS treated mice also respond in vitro more vigorously than controls to a T cell mitogen (Con A) but not at all differently from controls to a B cell mitogen (LPS). The stimulated cells are sensitive to anti theta serum + C' (experiment done with Swiss mice) and the Lyt 1,1 monoclonal antibody + C' (experiment done with C3H/HeN mice), indicating them functionally to be of T-helper variety. Unlike MHS, lipid A administration i.p. resulted in MHS like response in C3H/HeN but not in C3H/HeJ mice. MHS action has been traced to an induction of IL1 release by macrophages of MHS treated animals by chromatographic analysis of macrophage derived supernatants. IL1, in turn, according to the prevalent concepts would stimulate immature T cells to become mature IL2 producer cells, allowing T helper cell proliferation through IL2 release.

Modulation of the growth of murine thymoma cell lines having different Lyt-phenotypes by MDP and MDP(D-D): macrophage-mediated inhibition of in vitro cell growth

The ability of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) and its adjuvant-inactive stereoisomer, N-acetylmuramyl-D-alanyl-D-isoglutamine, (MDP(D-D] to inhibit the in vitro growth of 3 murine ascitic thymoma lines, expressing different Lyt-phenotypes, was studied. MDP inhibited the growth of all 3 cell lines. MDP(D-D) inhibited the 2 cell lines expressing Lyt-1+2- or Lyt-1+2+ phenotypes, but not the third cell line which expressed the Lyt-1-2+ phenotype. The ability of MDP or MDP(D-D) to inhibit thymoma growth was lost when the ascitic cell populations were depleted of macrophages. MDP could be replaced by a supernatant derived from an ascitic Lyt-1+2- cell population exposed to MDP. The supernatant required the presence of macrophages for activity. The inhibition by MDP of the growth of the Lyt-1-2+ cell line was prostaglandin synthetase dependent: indomethacin antagonized the inhibitory activity of MDP. The inhibition by MDP of the Lyt-1+2- cell line was partially antagonized by indomethacin, and no antagonism was observed with the Lyt-1+2+ cell line.

Stimulation of chemiluminescence and resistance against aerogenic influenza virus infection by synthetic muramyl dipeptide combined with trehalose dimycolate

The effect on respiratory burst of splenic cells from mice pretreated with oil-in-water emulsions of muramyl dipeptide (MDP), trehalose dimycolate (TDM), or the combination of MDP with TDM was studied by luminol-dependent chemiluminescence in response to stimulation by zymosan. Spleen cells from mice pretreated with TDM, but not those of mice treated with MDP, generated increased chemiluminescence. Spleen cells from animals pretreated with the combination of MDP and TDM exhibited markedly enhanced chemiluminescence activity. The effect of enhanced activity of preparations containing MDP combined with TDM was further examined in vivo by an aerosol infection of pretreated mice with a mouse-pathogenic influenza virus. Pretreatment with 6-O-acyl analogs and one ubiquinone derivative of MDP alone did not induce any resistance against influenza virus. Significant protection was conferred only when MDP and certain analogs were combined with TDM. The enhancement of nonspecific resistance to influenza virus infection was related to the chemical structure of the synthetic immunostimulant. A greater degree of protection was induced by the combination of TDM with the lipophilic derivatives like B 30-MDP and L-18 MDP.

Physicochemical properties of T-cell-activating monokines in guinea pigs

T-cell-activating monokines of guinea pigs with interleukin 1-like activity were produced in protein-free medium by stimulation of peritoneal macrophages with synthetic muramyl dipeptide (MDP). Gel filtration of the culture supernatant of MDP-stimulated macrophages revealed that most of the activity to potentiate the responses of thymocytes and lymph node T cells to phytohemagglutinin were found in the high-molecular-weight (40,000-80,000) fraction. By isoelectric focusing, the monokine in the high-molecular-weight fraction was focused at a pI of around 4.7 forming a somewhat broad band, indicating some heterogeneity. In the analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the high-molecular-weight fraction, the peak of the activity was found at an approximate Mr of 60K under unreduced as well as reduced conditions. Accordingly, it is likely that the monokine in this fraction is a polypeptide of 60K, but a possibility still remains that the 60K component is an aggregate of low-molecular-weight monokine which requires more rigorous conditions for dissociation.

Stimulating effect of MDP and its adjuvant-active analogues on guinea pig fibroblasts for the production of thymocyte-activating factor

Synthetic muramyl dipeptide (MDP) could stimulate skin fibroblasts of the guinea pig to produce thymocyte-activating factor, which augments the proliferative response of thymocytes to phytohemagglutinin (PHA). Adjuvant-active analogues of MDP also stimulated fibroblasts to produce the factor, whereas adjuvant-inactive analogues failed to do so. Thus a marked parallelism was found between adjuvant activity of these compounds and the stimulating effect on fibroblasts. Thymocyte-activating factor derived from MDP-stimulated fibroblasts was found in the fraction of mol wt 30,000-60,000 by gel filtration on a Sephacryl S-200 column. Furthermore, this factor did not exhibit T cell growth factor activity.

Stimulation of chemiluminescence by synthetic muramyl dipeptide and analogs

The effect on respiratory burst of murine splenic cells after in vitro exposure to synthetic muramyl dipeptide (MDP) and 6-O-acyl and quinonyl derivatives was studied at an early phase of interaction by luminol-dependent chemiluminescence (CL) in response to stimulation by zymosan. The MDP molecule enhanced CL, but the degree of CL response varied with the kinds of fatty acids introduced in the chemical structure of synthetic glycopeptide analogs. A 6-O-acyl derivative possessing an alpha-branched fatty acid chain, B30-MDP, stimulated maximum levels of CL activity. High CL responses were obtained with L8-MDP having a short chain of linear fatty acids and with QS-10-MDP-66 containing a ubiquinone compound. CL was also stimulated by MDP and its analogs in the spleen cells of nude mice lacking mature T lymphocytes, but the extent of stimulation was decreased compared with that of normal spleen cells.

Enhancement of antigen-specific suppression by muramyl dipeptide

The effect of the synthetic adjuvant MDP (N-acetyl-muramyl-L-alanyl-D-isoglu-tamine) on the generation of antigen-specific suppression was investigated. Suppression of the anti-bovine serum albumin response, which was achieved by intravenous administration of a peptic fragment of the antigen, was greatly enhanced by simultaneous administration of MDP. Induction of suppression by a combination of bovine serum albumin fragments and MDP was found to be antigen specific and appeared to occur via the generation of antigen-specific suppressor T cells.

Muramyl dipeptides: prospect for cancer treatments and immunostimulation

The immunopharmacological activities of bacterial cell walls and muramyl peptides were collected in table form with a comprehensive literature. The past and present studies emphasizing the host-defense enhancing activities of muramyl peptides for antitumor immunotherapy were surveyed along three possible approaches: 1) the nonspecific enhancement of natural defense ability of host against tumor cells themselves; 2) the enhancement of nonspecific resistance of host to microbial infections which are frequently encountered and difficult to treat in the advanced stage of tumor patients; and 3) the stimulation of immunity against tumor-specific or tumor-associated immunogens. Finally, the prospects of successful antitumor immunotherapy with muramyl peptides and their derivatives was discussed.

Biological activities of guinea pig mitogenic factor from immune lymphocytes stimulated with antigen

Mitogenic factor was produced by sensitized guinea pig lymph node cells stimulated with a specific antigen. Both T lymphocytes and macrophages were required for the production of this factor. The culture supernatant of lymphocytes containing the mitogenic factor exhibited a strong helping effect on the proliferative response of T lymphocytes to phytohemagglutinin (PHA). Mitogenic factor and the factor with the helping activity coeluted in the molecular weight range of 25,000-35,000 daltons in gel filtration. Furthermore the fraction containing mitogenic factor was found to support the proliferation of lymphoblasts induced by PHA or antigen, suggesting that the mitogenic factor may be the guinea pig equivalent of T cell growth factor (TCGF) reported in the mouse, rat, and human. On the other hand, the T cell-activating monokine of the guinea pig, possessing the helping activity for the proliferative response of T lymphocytes to PHA, never exhibited TCGF-like activity.

Stimulation of migration of human monocytes by bacterial cell walls and muramyl peptides

Bacterial cell walls, water-soluble fragments of the wall peptidoglycan, N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), and 6-O-acyl derivatives of MDP were examined for migration-stimulating activity on human peripheral blood monocytes by using a multiwell chemotaxis assembly. Cell walls isolated from 11 bacterial species caused a definite increase in monocyte migration, but the walls of Micrococcus lysodeikticus were scarely active. The migration-enhancing activity of Staphylococcus epidermidis cell walls was retained by a monomer as well as a polymer of disaccharide peptides which were prepared by digestion of the peptidoglycan with enzymes. It was finally revealed that the migration of monocytes was enhanced by MDP. 6-O-Octadecanoyl-MDP, 6-O-(2-tetradecylhexadecanoyl)-MDP, and 6-O-(3-hydroxy-2-docosylhexacosanoyl)-N-acetylmuramyl-L-seryl-D-isoglutamine were active, but to a lesser extent. A checkerboard assay demonstrated that the increased monocyte migration caused by S. epidermidis cell walls was directed toward a positive stimulus (chemotaxis).

Immunomodulation in guinea pigs by porcine spleen cell dialysate

The effect of porcine spleen dialysate was studied on delayed-type hypersensitivity reactions, as well as on the phagocytic capacity and intracellular prostaglandin levels of peritoneal macrophages. Porcine spleen cell dialysate was fractionated on Sephadex G-10 and these fractions, as well as unfractionated dialysate, were injected intraperitoneally into antigen-primed guinea pigs. The guinea pigs were tested for delayed-type hypersensitivity towards PPD and SK-SD. The results show that unfractionated spleen cell dialysate augmented slightly the delayed-type hypersensitivity reactions, and after fractionation a significant augmentory activity was detected in two adjacent, early eluting fractions. This active elution region corresponds to the elution region where most of the guinea pig DTH augmenting activity of leukocyte dialysate is also detected. Furthermore, these fractions significantly augmented the phagocytic capacity of peritoneal macrophages, and decreased the intracellular levels of prostaglandin PGE2, thromboxan B2 and prostacyclin. These results indicate that porcine spleen cells from non-immunized animals can be used as a source for a non-specifically acting immunomodulatory preparation, which resembles that found in human leukocyte dialysate. These immunomodulatory substance(s) seem to operate via monocyte activation.