Tumour-induced suppression of immune response and its correction

Immunosuppressive features of tumour cells are a major obstacle for immunotherapy of cancer. We recently noted that RENCA cells effectively interfere with the in vivo activation of RENCA-specific T cells. To unravel the underlying mechanism, we evaluated the influence of RENCA cells on a mixed-lymphocyte/ tumour reaction as well as an allogeneic mixed-lymphocyte reaction. We observed that RENCA cells were not directly immunosuppressive. Instead, they initiated deviation of an immune response in at least two independent directions: (i) expansion of a population of NK1.1+/CD3+ cells, which was accompanied by elimination of mainly CD4+ lymphocytes, and (ii) production of a leukocyte-derived inhibitory factor. Expression of the costimulatory molecule B7.1 by RENCA cells prevented induction of anergy, while expression of MHC class II molecules prevented expansion of NK1.1+ cells, which was accompanied by a significant decrease in cell death. Hence, an unimpaired response was observed only when RENCA cells expressed B7.1 plus MHC class II molecules. Thus, even if a tumour itself is not immunosuppressive, it can induce a strong deviation of the immune response. It is concluded that the first contact between elements of the immune system and the tumour cell can confer a severe bias on immunoregulatory circuits.     

Feedback suppression of the immune response in vivo. I. Immune B cells induce antigen-specific suppressor T cells

Stimulated lymphocytes are capable of synthesizing and secreting a variety of lymphokines which can affect the functions of several types of target cells. We report here the existence of a soluble factor released by activated human mononuclear leukocytes which produces a selective inhibition of human pulmonary fibroblast migration. This fibroblast migration inhibitory factor (FIF) was produced by antigen- or mitogen-stimulated human peripheral blood mononuclear leukocytes (PBML) and purified T cells. It inhibited the migration of ⁵¹Cr-labeled fibroblasts in a dose-dependent fashion with optimal effect (65–70% inhibition) obtained at 1:10 dilution and 8–20 hr of incubation. Sephadex G-100 fractionation revealed most activity to be found between 28,000 and 34,000 daltons. FIF was stable at 56 °C for 15 min, but destroyed at 80 °C or at low pH. This factor may play an important role in the modulation of fibrogenesis and healing processes by the immune system.     

Behaviorally conditioned suppression of the immune response by antilymphocyte serum

Previous studies have shown that cyclophosphamide, a drug with a broad spectrum of cytotoxic activity and one that produces noxious gastrointestinal side effects, can elicit taste aversion conditioning when paired with a non-immunosuppressive oral stimulus (saccharin) resulting in immunosuppression after subsequent exposure to the paired stimulus (1). The study reported here indicates that rabbit anti-rat lymphocyte serum (ALS) which is selectively cytotoxic for lymphocytes and does not produce sensory side effects can similarly induce taste aversion conditioning of the immune response. Rats were exposed to oral saccharin paired with ALS injection. Upon subsequent reexposure to saccharin alone the immunosuppressive effects of ALS were reenlisted and the primary mixed lymphocyte culture response of conditioned rats to allogeneic lymphocytes was suppressed by 35% compared to controls. The demonstrated influence of psychologic factors on the immune response has far reaching implications, especially to human medicine, and their role in the course of disease and recovery in man demands further investigation.     

Activation and suppression of the proinflammatory immune response by Vibrio cholerae toxins

Vibrio cholerae induces either non-inflammatory diarrhea or inflammatory gastroenteritis, depending on the presence of cholera toxin, a fluid secretion inducer and a modulator of host immunity. In the absence of cholera toxin, other toxins induce inflammation, resulting in gastroenteritis. Thus, multiple toxins likely affect the safety of live attenuated vaccines.     

Analysis of certain mechanisms of antigen-specific suppression of the immune response

CBA mice were immunized with sheep red blood cells (SRBC) to obtain immune spleen cells (ISc) which were used to suppressor cells. Administration of ISC to intact syngeneic recipients on the immunization day led to a more powerful suppression of the immune response as compared to that seen one day after antigen injection. Four days after immunization the animals' immune response was not liable to be suppressed. ISC extract possessed similar effects with respect to the immune response of normal spleen cells which were transplanted to the cyclophosphamide-treated recipients. The immune response of spleen cells from mice immunized with SRBC in a dose of 10(6) was less liable to be suppressed. Hyperimmune spleen cells from donors immunized with SRC in a dose of 10(9) were insensitive to ISC or to the extract. Experiments with the use of adoptive transfer of a mixture of immune and intact T- and B-cells have disclosed that B-cells from hyperimmune donors were resistant to suppression. Therefore, B-lymphocytes are the most probable target cells exposed to T-suppressors in the given system. The mechanism is discussed of the selective effect of T-suppressors on B-cells in the course of the immune response development during immunization with high doses of antigen.     

Corticosteroid-induced suppression of murine B cell immune response antigens

The quantitative variation in expression of B cell surface immune response-associated antigens (sIa) that is induced by in vivo i.v. administration of dexamethasone was studied by flow microfluorometry. Injection of 40 micrograms of dexamethasone resulted in a 35 to 40% reduction in the expression of sIa within 3 hr, reached its maximum effect within 6 hr, which on average resulted in 75% suppression of control values of sIa, and by 12 hr after injection began returning towards baseline levels. The suppressive effect of dexamethasone on B cell sIa was dose dependent with respect to the length of time required to reach maximal suppression, as well as with respect to the duration of suppression that was attained. When injections of dexamethasone were repeated on consecutive days, no additional increase in the level of sIa suppression achieved was observed. B cell sIa was also diminished after injection of dexamethasone into athymic nude mice, which suggests that the suppressive effect of dexamethasone on B cell expression of sIa is not a T cell-dependent phenomenon. Taken together, these data suggest that the suppression of B cell sIa by corticosteroids may be a means whereby endogenous or exogenous corticosteroids are able to influence the normal as well as abnormal immunologic state.     

Immune response and immune tolerance to the O-antigen of Shigella flexneri VI

The method for the determination of the number of cells synthetizing antibodies to S. flexneri VI O-antigen in the spleen of mice has been developed. Primary immune response to this antigen has been studied with the use of the new method. Immune response to the optimum immunogenic dose of O-antigen has a manifest variable character. The intensity of primary immune response has been shown to rise with the increase of the dose of O-antigen from 0.004 to 50 micrograms. The preliminary injection of 200 micrograms of O-antigen, followed by the injection of cyclophosphamide 2 days later, leads to the development of specific immunological tolerance to O-antigen in experimental animals.     

Effect of tolerance and of antibody mediated immune suppression on the avidity of the cellular and humoral immune response

Partial tolerance induction in adult rabbits although resulting in a marked depression of circulating antibody concentration, had no effect on either the avidity of the antibody synthesized at 2 weeks after immunization or the magnitude of the response of lymph node cells to stimulation by antigen in culture. A modest depression in the avidity of the cells responding to antigen in culture by an increase in thymidine incorporation was observed. Partial antibody mediated immune suppression was found to result in an increase in avidity of the residual circulating antibody and had no effect on the magnitude of the proliferative response induced by antigen in culture. Thus suppression appears to affect predominantly B-lymphocytes.     

LPS regulation of the immune response: suppression of immune responses to orally administered T-independent antigen

The regulation of immune responses to gastrically administered TI antigens has been investigated, and the characterization of a regulatory cell population has been performed. Intragastric administration of TNP-haptenated homologous erythrocytes (TNP-MRBC) induced splenic IgM anti-TNP PFC responses in LPS nonresponsive C3H/HeJ mice that were higher than those in LPS-responsive C3H/HeN mice and similar to those noted in athymic (nu/nu) C3H/HeN animals. The simultaneous intragastric administration of LPS with TNP-MRBC augmented immune responses in a manner similar to that previously reported for parenterally administered LPS and antigen. Further, LPS-induced augmentation of TNP-MRBC responses was greater in athymic mice. These findings were substantiated using in vitro spleen cultures. Intragastric challenge with a 2nd TI antigen, TNP-LPS, induced approximately 8-fold higher splenic anti-TNP PFC responses in athymic C3H/HeN mice compared with those in euthymic littermates. By admixture of B and T cell populations, it was demonstrated that the host responsiveness to TNP-LPS was negatively regulated by suppressor cells. Suppressive activity resided in a Thy 1.2-bearing, irradiation-resistant, nylon wool-nonadherent cell population. These cells could be demonstrated in spleen and Peyer's patches from young or old LPS-responsive C3H/HeN mice, but not in tissues from LPS nonresponsive C3H/HeJ mice. The specificity of the regulator cells was not limited to TNP-LPS responses, since immune responsiveness to another TI antigen, TNP-dextran, was also under the control of this cell population. These studies confirm the TI nature of TNP-MRBC and indicate that immune responses to gastrically administered antigens such as TNP-LPS, TNP-dextran, and possibly TNP-MRBC are negatively regulated by a suppressor T cell population. A role for endogenous LPS in the generation of regulator cells and the effect of these cells on host responses to gut-derived antigens is discussed.     

Cyclophosphamide-induced specific suppression of the protective immune response to rodent malaria.

Nonspecific and specific chemosuppression of the immune response to Plasmodium berghei protective antigens were investigated. Specific immunosuppression was defined operationally as the selective suppression of the protective response to the parasite in mice injected with a combination of gamma-irradiated infected mouse erythrocytes (gammaPb) and cyclophosphamide (CY) with continued responsiveness to sheep erythrocytes (SRBC). After initial treatment (gammaPb + CY), mice were injected with gammaPb in potentially immunogenic doses. These and appropriate control animals were later challenged with nonirradiated infected mouse erythrocytes. The influence of the initial treatment regimens on the protective response was evaluated by parasitemia, and mortality was observed after challenge. Specificity of suppression was measured by evaluating the ability of mice to produce antibody to SRBC. Both specific and nonspecific suppression of the protective response to malaria were noted. Initial treatment with drug alone resulted in increased parasitemia and mortality and suppression of the SRBC antibody synthesis in drug-pretreated immunized mice as compared with immunized mice not pretreated with the drug. On the other hand, suppression of the response to the parasite, but not to SRBC, in animals pretreated with gammaPb + CY was clearly greater than that induced by drug alone. Thus, animals treated with malarial antigen and cyclophosphamide develop a measurable specific immunosuppression. These studies indicate that immunity to malaria is influenced by both cyclophosphamide alone (general immunosuppression) and cyclophosphamide in combination with antigen (specific immunosuppression) in a manner analogous to other immune responses.     

Lipopolysaccharide-induced suppression of the primary immune response to a thymus-dependent antigen.

The immune response to a thymus-dependent antigen was depressed in vivo and in vitro in spleen cells from mice injected with LPS i.p. a few days before challenge with the antigen. Spleen cells from LPS-injected mice could, however, respond with increase DNA synthesis after activation with polyclonal B and T cell activators in vitro. The LPS-activated spleen cells could actively suppress normal cells in their response to the antigen sheep red blood cells. The suppressor cells contained in the LPS-activated spleens were most likely B lymphocytes, and the possible mechanism for their inhibitory function is discussed.     

Parasite-induced suppression of the immune response in Aedes aegypti by Brugia pahangi

The melanization response against intrathoracically inoculated Brugia pahangi and Dirofilaria immitis microfilariae (mff) isolated from vertebrate host blood was evaluated in both uninfected Aedes aegypti black-eyed Liverpool strain and in mosquitoes harboring a developing B. pahangi infection. The immune response against inoculated mff of either species was significantly reduced by 28-47% in infected as compared with uninfected mosquitoes. Attempts to passively transfer this suppression factor(s) by inoculating naive mosquitoes with 0.1-0.2 microliter of hemolymph from B. pahangi-infected mosquitoes produced equivocal results. The role this parasite-induced immune suppression might play in aiding parasite survival in compatible vectors is discussed.     

Induction of the immune response suppression in mice inoculated with Candida albicans

There is a controversy in respect to the immunological response (humoral or cellular) concerning the defense against Candida albicans. Candidosis would induce sub-populations of suppressor cells in the host cell-immune response. This report tries to show the effect of different doses of C. albicans (alive or heat-killed) on the expression of cell-mediated and humoral immunity. The effect upon cell immunity was determined by inoculating different lots of singeneic mice, doses of varied concentration of C. albicans and checking for delayed-type hipersensitivity (D.T.H.). D.T.H. was also controlled in syngeneic normal mice which had previously been injected with inoculated mice spleen cells. Humoral immunity was assayed by measuring the induced blastogenesis by Pokeweed Mitogen on spleen mononuclear cells with different doses of C. albicans. Results obtained show that the different doses gave origin to: Suppression of humoral and cell response (10(8) alive); Suppression of only humoral response (10(6) alive); Suppression of cell response and increase of humoral response (10(9) dead); Increase of both responses (10(8) dead).     

Active suppression of the pulmonary immune response by Francisella tularensis Schu4

Francisella tularensis is an obligate, intracellular bacterium that causes acute, lethal disease following inhalation. As an intracellular pathogen F. tularensis must invade cells, replicate, and disseminate while evading host immune responses. The mechanisms by which virulent type A strains of Francisella tularensis accomplish this evasion are not understood. Francisella tularensis has been shown to target multiple cell types in the lung following aerosol infection, including dendritic cells (DC) and macrophages. We demonstrate here that one mechanism used by a virulent type A strain of F. tularensis (Schu4) to evade early detection is by the induction of overwhelming immunosuppression at the site of infection, the lung. Following infection and replication in multiple pulmonary cell types, Schu4 failed to induce the production of proinflammatory cytokines or increase the expression of MHCII or CD86 on the surface of resident DC within the first few days of disease. However, Schu4 did induce early and transient production of TGF-beta, a potent immunosuppressive cytokine. The absence of DC activation following infection could not be attributed to the apoptosis of pulmonary cells, because there were minimal differences in either annexin or cleaved caspase-3 staining in infected mice compared with that in uninfected controls. Rather, we demonstrate that Schu4 actively suppressed in vivo responses to secondary stimuli (LPS), e.g., failure to recruit granulocytes/monocytes and stimulate resident DC. Thus, unlike attenuated strains of F. tularensis, Schu4 induced broad immunosuppression within the first few days after aerosol infection. This difference may explain the increased virulence of type A strains compared with their more attenuated counterparts.     

Morphogenesis and histophysiology of the corpus luteum

A great amount of different problems on morphogenesis and histophysiology of the corpus luteum is presented, with an emphasis on light optic and ultrastructural data that characterize the developmental dynamics of the corpus luteum. The vascular reaction is described in details, beginning from the preovulatory period. The total high vascularization rate is demonstrated and certain information on ultrastructure of newly formed capillaries and macrophages is concerned with. For the first time the authors' data on intravascular macrophages are given. The role of macrophages in the function and structural dynamics of the corpus luteum is discussed. Owing to the results obtained histochemically, ultrastructurally and biochemically, the subject on dynamics of the corpus luteum hormonoproduction, on processes participating in the hormone secretion, as well as on the role of the interstitial tissue in the corpus luteum formation is considered. The data from the literature and those of the authors are presented concerning the means and ways of progesteron transport in the form of vesicles, granules, or by means of molecular diffusion. Participation of the corpus luteum macrophages (tissue and vascular ones) in processes of synthesis and transport of progesteron is analysed. The role of prostaglandins in the chain of regulation of development, function and involution of the corpus luteum is studied. The changes in balance of prostaglandins, when prostaglandin F2 is administered result in decreasing amount of progesterone in blood. In the experiment, synthesis of prostaglandins is blocked by indometacin administration and it causes certain disturbances in luteal transformation.     

Antigen-nonspecific suppression of the immune response in mice as affected by pertussis vaccine

A study was made of the suppressorgenic action of killed whole-cell pertussis vaccine prepared from B. pertussis strains 475 and 305. Thymic and splenic lymphocytes of CBA mice 3-7 days following intraperitoneal or intravenous inoculation of pertussis vaccine were shown to inhibit in an antigen-nonspecific manner the plaque-forming cell (PFC) production in the adoptive transfer experiments. Suppression of graft-versus-host reaction was also observed, estimated by the survival of irradiated (CBA X C57BL/6) Fl mice, or by measuring the endogenous colony formation. Suppression-mediating cells were found to be susceptible to complement-dependent lysis by the anti-I-Jk alloantiserum against the specific marker of suppressor T cells, antigen I-J. Furthermore, thymocytes of pertussis vaccine-treated mice were shown to inhibit the endogenous colony formation in syngeneic mice irradiated in sublethal dose. Thus, B. pertussis vaccination of CBA mice resulted in appearance of suppressor T cells that exerted various inhibitory activities in several experimental test-systems.