Mycoplasma-associated immunosuppression: effect on hemagglutinin response to common antigens in rabbits

Exosomes released from Mycoplasma infected tumor cells activate inhibitory B cells

Mycoplasmas cause numerous human diseases and are common opportunistic pathogens in cancer patients and immunocompromised individuals. Mycoplasma infection elicits various host immune responses. Here we demonstrate that mycoplasma-infected tumor cells release exosomes (myco+ exosomes) that specifically activate splenic B cells and induce splenocytes cytokine production. Induction of cytokines, including the proinflammatory IFN-γ and the anti-inflammatory IL-10, was largely dependent on the presence of B cells. B cells were the major IL-10 producers. In splenocytes from B cell deficient μMT mice, induction of IFN-γ+ T cells by myco+ exosomes was greatly increased compared with wild type splenocytes. In addition, anti-CD3-stimulated T cell proliferation was greatly inhibited in the presence of myco+ exosome-treated B cells. Also, anti-CD3-stimulated T cell signaling was impaired by myco+ exosome treatment. Proteomic analysis identified mycoplasma proteins in exosomes that potentially contribute to the effects. Our results demonstrate that mycoplasma-infected tumor cells release exosomes carrying mycoplasma components that preferentially activate B cells, which in turn, are able to inhibit T cell activity. These results suggest that mycoplasmas infecting tumor cells can exploit the exosome pathway to disseminate their own components and modulate the activity of immune cells, in particular, activate B cells with inhibitory activity.

Chinese medicinal herbs reverse macrophage suppression induced by urological tumors

Tumors are known to produce factors suppressing macrophage function. In this study we demonstrated in vitro suppression of macrophage chemiluminescent oxidative burst associated with viable cells and cell-free extracts of two urological neoplasms--murine renal cell carcinoma (Renca) and murine bladder tumor (MBT). Suppression was reversed by extracts of two Chinese medicinal herbs, Astragalus membranaceus (AM) and Ligustrum lucidum (LL). Murine macrophage cell line J774 was incubated with either the viable tumor cells or the cell-free tumor extract for 18 hours at 37C and 5% CO2. Chemiluminescent oxidative burst as an indicator of macrophage function was triggered by adding zymosan A suspension containing luminol and assayed in an automated luminometer. Photon emission over time was counted and the results were expressed as integrated photon emission. Significant dose-related depression of oxidative burst occurred with either the viable tumor cells or the cell-free tumor extracts. Depression was partially or completely reversed by the presence of 50-100 micrograms./ml. of either the AM or the LL extract. AM and LL have previously been shown to modulate immune response. Data from this study suggest that they may also exert their antitumor activity via abolition of tumor-associated macrophage suppression.

The regulation of murine B cell differentiation. I. Nonspecific suppression caused by Mycoplasma arginini

During the screening of suppressor T cell (Ts) hybridomas for antigen-nonspecific suppressive activity, we isolated a strain of Mycoplasma arginini which inhibits B cell antibody production in vitro. The addition of mycoplasma-containing Ts hybridoma culture supernatant to splenic B cells responding to sheep red blood cells (SRBC) and T cell-replacing factor or to trinitrophenyl-lipopolysaccharide (TNP-LPS) suppressed the production of anti-SRBC and anti-TNP plaque-forming cells in a dose-dependent and antigen-nonspecific manner. Inhibition occurred due to the noncytotoxic mycoplasmal infection of B cells in culture and required the physical presence of microorganisms. Cell cycle analysis of acridine orange-stained B cells indicated that mycoplasmal infection did not block cell cycle entry and progression of antigen-activated cells. In addition to a suppressive activity, this strain of mycoplasma was selectively mitogenic for B cells. Furthermore, the mycoplasma failed to stimulate or inhibit T cell proliferation. The suppressive and mitogenic activities were selectively absorbed by mitogen-activated B cells but not T cells. These results indicate that this strain of M. arginini mimics the suppressive activity of an antigen-nonspecific Ts factor selective for B cell antibody production.

Effect of corynebacterium parvum in the induction and course of mycoplasma arthritis of mice

The effect of the immunostimulant C. parvum on the establishment and course of mycoplasma arthritis of mice was investigated. Male Swiss albino mice were injected intra-venously with M. arthritidis culture and intraperitoneally with C. parvum. It was shown that mice immunostimulated with C. parvum were significantly protected against the establishment of arthritis if the mycoplasma was given 9 days after the immunostimulant. However, when the arthritis was established C. parvum had no effect on the course of the arthritis. A close association between mycoplasma arthritidis and synovial cells in proposed as a possible explanation of this observation.

Mycoplasma pulmonis arthritis in congenitally athymic (nude) mice. Histopathological features

Histopathological examinations were performed on arthritis joints and other organs of strain BALB/cA nu/nu and nu/+ mice intravenously injected with Mycoplasma pulmonis strain m53. In both groups of mice suffering from polyarthritis, acute inflammatory lesions with infiltration of polymorphonuclear leukocytes in the synovia and periarticular tissues were observed one to two weeks after injection. In nu/nu mice, the acute inflammation appeared repeatedly up to 20 weeks after inoculation, when the experiment was terminated, and furthermore, extensive synovial and periarticular necrosis were characteristically present after the 4th week. Only a small number of lymphocytes and plasma cells were in the lesions. In nu/+ mice, after the early acute inflammation of arthritis, relapses of the infiltration of polymorphonuclear leukocytes were also observed in some mice in and after the 10th week. In addition, infiltration of lymphocytes and plasma cells were substantial after the 15th week. Focal necrosis was sometimes found in the liver of nu/nu mice. Perivascular infiltration of small lymphocytes and plasma cells was found in the lungs, liver and kidney of nu/+ mice in and after the 15th week. Repair mechanisms of injured articular tissues in nu/nu mice were histopathologically poor, while those in nu/+ mice seemed to be progressive and quite similar to those reported by many investigators for mice with the thymus intact. The histopathological differences are discussed in respect to the thymus-dependent immune responses.

Mycoplasma pulmonis arthritis in congenitally athymic (nude) mice. Clinical and biological features

Congenitally athymic BALB/cA nu/nu mice were employed to elucidate the role of the thymus in experimental Mycoplasma pulmonis strain m53 infection, and nu/+ mice were used for comparison. Chronic polyarthritis was frequently produced in both of nu/nu and nu/+ mice by intravenous injection of the organisms. Macroscopically, nu/nu mice developed severer arthritis and a much lower grade of resolution than nu/+ mice. Periarticular abscess, conjunctivitis, and emaciation were observed in some of the nu/nu mice, but not in the nu/+ mice. Mycoplasmas were isolated from joints and other tissues (including periarticular abscesses and eyelids) of infected nu/nu mice at higher frequencies as well as in greater quantities, and did not show any elimination trends for at least 20 weeks after inoculation. However, nu/+ mice, mycoplasmas were almost exclusively located in joints, and distribution of organisms to the other organs disappeared soon after the infection. Increases in complement-fixing antibody titers were not related to the inhibition of mycoplasmal spread. Thymus-dependent functions that may in some way prevent growth and spread of mycoplasmas in mice are discussed.

Mycoplasma-dependent activation of normal lymphocytes: induction of a lymphocyte-mediated cytotoxicity for allogeneic and syngeneic mouse target cells

Mycoplasma arthritidis, M. hominis, and M. arginini were tested for their ability to induce a cytotoxic response from normal CBA mouse lymphocytes against 51Cr-labeled allogeneic target cells. In most cases, the mycoplasmas alone were not toxic for the target cells. Furthermore, the mycoplasmas did not result in decreased lymphocyte viability but, in fact, contributed to enhanced lymphocyte survival. In the absence of normal CBA lymphocytes, mycoplasmas alone did not induce a significant amount of cell damage in either the allogeneic or the syngeneic target cells. Strains of M. arthritidis and M. hominis, when added to the lymphocyte-target cell mixtures, induced statistically significant increases in 51Cr release from both target cell types at each assay period after 6 h. The release of 51Cr was taken as a measure of cell death. M. arginini induced only low levels of cytotoxicity or none at all. Both arthritogenic and non-arthritogenic strains of M. arthritidis induced the cytotoxic response. The degree of cytotoxicity produced was directly related to the size of the initial inoculum. The presence or absence of serum in the culture medium did not contribute significantly to the cytotoxicity response.

Mycoplasma-dependent activation of normal lymphocytes: mitogenic potential of mycoplasmas for mouse lymphocytes

Nonviable preparations of a wide variety of glucose-utilizing mycoplasma species, including Acholeplasma laidlawii and Spiroplasma citri, were found to be mitogenic for mouse lymphocytes. Particularly strong reactions were obtained with Mycoplasma synoviae, M. gallisepticum, M. pneumoniae, S. citri, and a strain of M. fermentans that was previously isolated from a leukemic patient. Nonviable preparations of arginine-utilizing mycoplasmas inhibited the uptake of [3H]thymidine by lymphocytes, but this effect could be reversed by heat treatment or arginine supplementation, and a stimulatory effect was then observed. Viable M. arthritidis was also found to have a mitogenic effect, as detected by an increased uptake of [3H]thymidine by normal lymphocytes and by autoradiographic techniques in which an increase in the numbers of transformed cells was seen. These observations provide the potential for enhanced immunological responsiveness or lymphokine-mediated inflammation in mycoplasma-infected hosts.

New models of chronic synovitis in rabbits induced by mycoplasmas: microbiological, histopathological, and immunological observations on rabbits injected with Mycoplasma arthritidis and Mycoplasma pulmonis

A dose-dependent chronic synovitis was induced in rabbit knees after the intra-articular injection of both Mycoplasma arthritidis and Mycoplasma pulmonis. The inflammation progressed from an initial acute phase at 1 week characterized by edema, infiltration of the synovium with monocytes and heterophils, and desquamation of lining cells, to a more chronic phase at 1 and 3 months, in which villus hyperplasia, lymph "nodules," mononuclear cell infiltration, fibroplasia, and collagen deposition were prominent. With one exception, mycoplasmas could no longer be cultivated from the joints 1 month postinoculation. Both mycoplasma species evoked a humoral antibody response that was more marked in synovial fluids than in peripheral blood. A cell-mediated immune reaction, as evidence by enhanced uptake by [3H]thymidine by sensitized blood, spleen, or node lymphocytes in the presence of homologous antigen, was detected only in rabbits injected with M. pulmonis. Lymphocytes taken from arthritic rabbits were no more cytotoxic toward synovial cells derived from normal or arthritic rabbits than were normal lymphocytes. The models of synovitis described in this study offer a convenient probe for determining the mechanisms of mycoplasma-induced inflammation, since they require only a single injection of the initiating agent and, in addition, utilize an animal host large enough for detailed investigation into the nature of mycoplasma/synovium interactions.

Enterobacterial common antigen

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Arthritis of mice induced by Mycoplasma arthritidis. Humoral antibody and lymphocyte responses of CBA mice

Peak arthritis occurred 7 days after intravenous injection of CBA mice with Mycoplasma arthritidis and persisted in some animals for 84 days. A marked leucocytosis was apparent for the first 21 days. Complement-fixing antibodies reached a peak 14 days after injection of the organisms and persisted at high levels for 84 days. Metabolic-inhibiting and mycoplasmacidal antibodies were present but at much lower titres.

Chronic proliferative arthritis of mice induced by Mycoplasma arthritidis: demonstration of a cell-mediated immune response to mycoplasma antigens in vitro

Lymphocytes taken from mice chronically infected with Mycoplasma arthritidis exhibited a significant blastogenic response as measured by (3H)thymidine uptake when exposed in vitro to M. arthritidis antigens. The lymphocytes taken from 9 of 12 control mice of similar age exhibited an inhibition of (3H)thymidine uptake when exposed to M. arthritidis antigens.

Serological comparison of five arginine-utilizing Mycoplasma species by two-dimensional immunoelectrophoresis

Five arginine-utilizing, nonglycolytic Mycoplasma species were compared serologically by two dimensional immunoelectrophoresis. The survey included: Mycoplasma hominis, Mycoplasma arthritidis, Mycoplasma gateae, Mycoplasma gallinarum, and three strains of Mycoplasma arginini. Although the M. arginini strains showed strong cross-reactions, each strain produced a different antigenic profile which was distinct and which indicated significant antigenic differences between strains. The M. arginini strains showed strong relationships with M. gateae; lesser cross-reactions were observed with other strains. Common antigens were demonstrable in the entire group. When all these species were compared with a glycolytic species, Mycoplasma gallisepticum, no cross-reactions were observed. Two-dimensional immunoelectrophoresis was a far more sensitive technique than double-immunodiffusion since as many as 20 components could be resolved.