Control of mitogen-induced transformation: characterization of a splenic suppressor cell and its mode of action

The biochemistry and medical significance of the flavonoids

Flavonoids are plant pigments that are synthesised from phenylalanine, generally display marvelous colors known from flower petals, mostly emit brilliant fluorescence when they are excited by UV light, and are ubiquitous to green plant cells. The flavonoids are used by botanists for taxonomical classification. They regulate plant growth by inhibition of the exocytosis of the auxin indolyl acetic acid, as well as by induction of gene expression, and they influence other biological cells in numerous ways. Flavonoids inhibit or kill many bacterial strains, inhibit important viral enzymes, such as reverse transcriptase and protease, and destroy some pathogenic protozoans. Yet, their toxicity to animal cells is low. Flavonoids are major functional components of many herbal and insect preparations for medical use, e.g., propolis (bee's glue) and honey, which have been used since ancient times. The daily intake of flavonoids with normal food, especially fruit and vegetables, is 1-2 g. Modern authorised physicians are increasing their use of pure flavonoids to treat many important common diseases, due to their proven ability to inhibit specific enzymes, to simulate some hormones and neurotransmitters, and to scavenge free radicals.

Effect of low dose recombinant interleukin 2 plus indomethacin on mortality after sepsis in a murine burn model

Under anaesthesia, 129 8-week-old male A/J mice were subjected to a 25 per cent scald or sham burn and then resuscitated. They were divided at random into two groups. Mice from the first group were allocated into two groups. Mice from the first group were allocated into four subgroups to receive 6 days intraperitoneal (I.P.) injections as follows: (i) recombinant human interleukin 2 (rhIL-2) (250 units day-1); (ii) saline; (iii) indomethacin (5 micrograms-1 day-1); or (iv) rhIL-2 (250 units) + indomethacin (5 micrograms). Sham burned mice served as no treatment controls. All animals were subjected to peritonitis induced by caecal ligation and puncture 10 days after the burn and mortality was assessed. Mice from the second group were allocated to two subgroups to receive 6 days intraperitoneal injections of: (i) rhIL-2 + indomethacin; or (ii) saline. Animals in this group did not undergo septic challenge. They were randomly killed on days 7, 9 or 10 after the burn. Their splenocytes were harvested and assayed for response to the mitogens phytohaemagglutinin (PHA) and concanavalin A (Con A), and for production of interleukin 2. Mortality rate in animals subjected to burn and septic challenge without treatment was 75 per cent; in mice receiving rhIL-2 alone it was 68 per cent, in mice receiving indomethacin alone it was 62 per cent (no significance) and in mice receiving rhIL-2 + indomethacin it was reduced to 38 per cent (P less than 0.02). Splenocytes from animals receiving combination therapy had markedly improved responses to PHA on days 7 (P = 0.01), 9 (P = 0.02), and 10 (P = 0.008), and to Con A on days 7 (P = 0.001), 9 (P = 0.002) and 10 (P = 0.001), after burn injury. Interleukin 2 production was also significantly (P = 0.004) improved by therapy with rhIL-2 + indomethacin. These data suggest that low dose rhIL-2 in combination with indomethacin may have potential use in the therapy of burn victims.

An intrinsic suppressor cell-controlling formation of autologous rosettes in peripheral mouse lymphocytes

The existence of intrinsic suppressor cell-controlling autologous rosette formation in mouse peripheral blood lymphocytes was demonstrated. This cell is glass adherent, Thy 1,2 positive, and loses its activity after treatment with monoclonal anti-Lyt 2 antibodies plus complement. Suppression of the autologous rosette formation also involves a factor released by these cells directed against autologous erythrocytes. The suppressive phenomenon is strain specific.

Differences in the effect of indomethacin and preincubation on the lymphoproliferative response to concanavalin A of spleen cells from low responder C57BL/6 and high responder BALB/c mice

In vivo treatment with 100 micrograms of indomethacin each 48 h for 2 weeks enhanced the proliferative response to concanavalin A (Con A) of spleen cells from mice of the C57BL/6 (B6) strain, low responder to T cell mitogens, but did not modify the response of spleen cells from mice of the high responder strain BALB/c (C). The enhancing effect of in vivo indomethacin treatment was more marked in cultures of B6 splenocytes stimulated with high, moderately supraoptimal doses of Con A than in cultures stimulated with optimal mitogen doses. Addition of indomethacin to cultures of spleen cells from untreated donors induced greater increase of the lymphoproliferative response of cells from low responder B6 than from high responder C mice. The enhancing effect of indomethacin added in vitro was observed in cultures stimulated by optimal but not by supraoptimal doses of Con A. The addition of indomethacin did not enhance the response of B6 spleen lymphocytes depleted of adherent cells. Preincubation for 24 h prior to mitogen stimulation increased the response to high Con A doses of spleen cells from low responder B6 mice whereas this procedure did not enhance lymphocyte proliferation in cultures of spleen cells from high responder C mice. Supplementation with indomethacin in vitro combined with preincubation induced additive enhancing effects on DNA synthesis by B6 spleen lymphocytes, suggesting that each treatment acts through different mechanism(s). The results indicated that spleen cells from low responder B6 strain mice are more sensitive than cells from high responder C mice to the potentiating effect of indomethacin and preincubation on the proliferative response to Con A. These observations suggest that mechanisms sensitive to indomethacin and to preincubation contribute to the depression of mitogen induced DNA synthesis in low responder B6 mice.

Requirement for prostaglandin E1 (PGE1) for the secretion of suppressor cell inducer factors by spleen cells of tumor-bearing mice

We have demonstrated previously that spleen cells from mice bearing M-1 fibrosarcomas release low molecular weight factors capable of activating suppressor cells from unprimed normal spleen cells. Using Marbrook vessels to separate inducer and precursor populations, we found in the previous paper that cyclooxygenase inhibitors blocked the activation of suppressor cells and that this activation could be restored by exogenous PGE1. In this paper we have examined the site of action of the prostaglandins in the activation of suppressor cells. To do so, we tested cell-free supernatants from cultured spleen cells of tumor-bearing mice (inducer cells) for the ability to activate suppressor cells from unprimed normal spleen cells (precursor cells). Supernatants from acetyl salicylic acid (ASA) treated inducer cells did not activate suppressor cells and exogenous PGE1 could not restore the activity of this supernatant. In contrast, if inducer cells were treated with ASA and then incubated with PGE1, the supernatant was capable of activating suppressor cells. No role for prostaglandins at the level of the precursor cells or the effector suppressor cells was seen. These data suggest that the inducer cells in tumor-bearer spleens require prostaglandins for the release of an inducer factor but that prostaglandins are not required for the action of this factor on the precursor cells or for the effector function of the activated suppressor cells.

Dietary fat and neoplasia--the role of net energy in enhancement of carcinogenesis: effects of fat and calories on the immune system

The mechanism by which carcinogenesis is enhanced by dietary fat is not understood. We know that a minimum level of essential fatty acids (EFA) is necessary for mammary tumor development and that this level probably exceeds the normal requirements of rats. Once the minimum level of EFA has been supplied, the calorie contribution of dietary fat may account for its enhancement of carcinogenesis. In this regard, we must recognize that the efficiency with which dietary energy is utilized is known to increase as the fat content of the diet is raised. Hence even when fed isocalorically to low fat diets, high fat diets will provide more net energy. Modulation of host immunity has been proposed as a mechanism of action of both fat and calorie intake on neoplasia. We review the literature examining the effects of fat and calories on the cell-mediated immune system, that arm of the immune system most directly responsible for the killing of neoplastic cells.

Prostaglandins, cyclic AMP production and biological activity of alloimmune thymocytes

The effect of alloimmunized non-adherent thymocytes on the spontaneous activity of the mouse atria was studied. BALB/c anti C3H non-adherent thymocytes induced negative inotropic effect on C3H atria. Cell-free supernatant from non-adherent thymocytes induced the same biological activity. This activity was blunted by the inhibition of non-adherent immune thymocytes' cyclo-oxygenase activity. PGE was present in higher amounts in free-cell supernatant from BALB/c anti C3H thymocytes plus C3H atria than in those from non-immune thymocytes. Intracellular levels of immune thymocytes cAMP are raised in comparison with those of normal thymocytes. It is proposed that alloantigen stimulates non-adherent thymocytes, increasing intracellular levels of cAMP and PGE. Immune thymocytes, release PGE upon recognition of the alloantigens expressed in the atria and this triggers a negative inotropic effect. The increment in immune thymocyte cAMP appears to be associated with the activation of thymocytes cyclo-oxygenase activity by alloimmunization.

Macrophage-mediated mitogenic suppression induced in mice of the C3H lineage by a vaccine strain of Salmonella typhimurium

Salmonella typhimurium, strain SL3235, an avirulent organism, has been used as a live vaccine in mice of the C3H lineage and has been found to confer high levels of protection. In the present study, it was found that intraperitoneal injection of approximately 5 X 10(5) live SL3235 induced potent suppression of spleen cell mitogenic responses to a panel of B- and T-cell mitogens in the Salmonella-hypersusceptible C3H/HeJ and C3HeB/FeJ, and the inherently resistant C3H/HeNCrlBR mice. Maximal suppression (greater than 99%) was seen at 1 week, and was still significant but waning (50%) at 3 weeks postimmunization. In contrast, cells of mice receiving acetone-killed cells were not suppressed. Removal of macrophages, but not T or B cells, restored responsiveness, indicating that suppression was macrophage mediated. Prostaglandins were not the major mediator of suppression, as in vitro administration of indomethacin failed to abrogate suppression. As mitogenic suppression occurred in mice with high levels of Salmonella immunity, the suppression is interpreted as a marker of a powerful immunomodulatory process induced by live cells, rather than as an indication of poor immune status of the host.

Suppression of B-cell and T-cell responses by the prostaglandin-induced T-cell-derived suppressors (PITS)--III. Production of PITS beta factors from T-cell hybridomas

Previous studies have shown that the prostaglandin-induced T-cell-derived suppressors (PITS) are actually a mixture of at least seven distinct factors. These factors may be reproducibly resolved by size-exclusion chromatography followed by high-pressure liquid chromatography (HPLC). Results are presented here which suggest that two T-lymphocyte hybridoma clones are capable of constitutive synthesis of three of these suppressor factors. Results show that clone Hyb-7SC2 produces factors which co-elute (by HPLC) with the PITS beta2 and PITS beta3 factors, while clone Hyb-9SC2 produces a factor which co-elutes with PITS beta1. These results suggest the possibility that the seven PITS beta factors are not the product of a single cell population.

Alterations in serum antibody and peripheral T-lymphocyte subsets resulting from treatment of murine immune complex glomerulonephritis with PGE2

The effects of treatment with 16,16-dimethyl prostaglandin E2 (DMPGE2) on histologic damage, glomerular immune complex deposition, serum total IgG subclass levels, anti-apoferritin IgG levels, and peripheral blood T-lymphocyte subsets were determined in apoferritin-induced immune complex glomerulonephritis of mice. The results demonstrate that doses of DMPGE2 ranging from 2.5 to 10 micrograms twice daily significantly reduced the degree of glomerular damage in a dose-dependent manner. Similarly, these doses of DMPGE2 reduced the amount of immunoglobulin deposition along peripheral capillary loops. Total IgM, IgG1, IgG2a, and IgG2b were unaffected by DMPGE2 administration. Serum anti-apoferritin IgG levels were significantly reduced in mice receiving DMPGE2 at doses of 5 and 10 micrograms twice daily. Nephrotic mice had significantly reduced peripheral blood total T lymphocytes (Lyt-1+) and a reduction of T-suppressor (Lyt-2+) cells. Administration of DMPGE2 at doses of 5 and 10 micrograms twice daily prevented these T-lymphocyte alterations. These studies indicate that treatment of mice receiving apoferritin with DMPGE2 may prevent glomerulonephritis by altering both cellular and humoral immune responses.

Suppression of B-cell and T-cell responses by the prostaglandin-induced T-cell-derived suppressor (PITS). II. Resolution of multiple PITS beta factors

It has been shown that T cells cultured with prostaglandin E2 are induced to release at least two peptide-containing lymphokines (PITS). Both the high-molecular-weight (35,000; PITS alpha) and the low-molecular-weight (2000 to 5000; PITS beta) factors were shown to be potent inhibitors of both T-cell- and B-cell-dependent mitogen responses. Data are reported here which show that the PITS beta factor may be reproducibly resolved into seven components by high-pressure liquid chromatography. Although each of these components is capable of suppressing the phytohemagglutinin-induced blastogenic response, not all of these factors will suppress the in vitro antibody response to sheep erythrocytes, or a mixed lymphocyte reaction. Nevertheless, the broad-range suppressive effects previously reported for PITS beta now seem to be mediated by multiple low-molecular-weight PITS factors.

Immunomodulating properties of two synthetic adjuvants: dependence upon type of antigen, dose, and time of administration

The effects of two synthetic adjuvants on the antibody response to sheep red blood cells (SRBC) as a thymus dependent (TD) antigen and to dinitrophenyl59-Ficoll as a thymus-independent (TI-1) antigen were investigated in mice. Both dimethyldioctadecylammonium bromide (DDA) and dextran sulfate (DXS) augmented the humoral response to SRBC but not to dinitrophenyl59-Ficoll if injected simultaneously with antigen. Dose-response curves of both antigen and adjuvant revealed that DXS compared to DDA is a more effective adjuvant for the induction of a humoral response to SRBC. Intraperitoneal injection of DDA or DXS evoked a sequence of distinct immune responsive states in mice, measured by the capacity to develop an anti-SRBC response. A short immune-potentiating period (less than 6 hr) is followed by a suppressive, second immune-potentiating state. The immune suppressive state lasted for a period of about 8 days and was restricted to TD-antigens. Suppression could be totally overridden by injection of DDA or DXS simultaneously with antigen, suggesting that the suppressive state was reversible. The kinetics of the observed alteration of the immune response by DDA and DXS were very similar. It is concluded that differences in the modulation of the immune response by DDA and DXS are limited to the initial state. Long-term effects like the induction of a succession of distinct immune responsive states, are more or less similar for both adjuvants. Possible mechanisms by which these immunomodulators interfere with the immune system are discussed.

Induction and amplification of T-lymphocyte proliferative responses to periodate and soybean agglutinin by human adult vascular endothelial cells

Human mononuclear phagocyte (M phi) populations were compared to adult human endothelial cells (HEC) for their respective abilities to influence the proliferative responses of purified human T lymphocytes to the mitogenic agents Na-m-periodate (IO-4), soybean agglutinin (SBA), or allogeneic cells. HEC and M phi were both capable of inducing proliferative responses of allogeneic T lymphocytes in mixed-lymphocyte culture. Under low cell density culture conditions, purified T-lymphocyte proliferative responses to IO-4 or SBA could be restored by addition of syngeneic M phi or HEC. At higher cell density culture conditions, proliferation of T cells to IO-4 could be amplified more by HEC than M phi. T-lymphocyte proliferative responses to SBA were amplified by addition of HEC but were suppressed by addition of M phi. These findings indicate that human adult HEC are unique and potent accessory cells for T lymphocytes. Furthermore, these findings demonstrate that accessory cell functions of HEC can be discriminated from those of M phi.

Suppression of polyclonal, tumor cell and alloantigen-induced proliferation: identification of cyclooxygenase pathway dependent and independent mechanisms

Polyclonal T cell activation, syngeneic tumor cell and alloantigen-induced proliferative responses were studied to determine if the regulation of these responses in normal and tumor-bearing NBR rats is mediated through products of the cyclooxygenase pathway and prostaglandin E2 (PGE2) in particular. Young rats and tumor-bearing rats have previously been shown to produce poor proliferative responses to PHA, Con A and syngeneic methylcholanthrene (MCA)-induced fibrosarcoma cells. The poor responses to PHA and Con A are mediated by PGE2 in unfractionated ( UNF ) and nylon wool adherent (ADH) cells. The same relationship was also established in the mixed leukocyte tumor cell (MLTC) response to MCA tumor cells although it appears to be of only minor significance as the enhancement following indomethacin (IND) treatment is still a relatively poor response. Indomethacin generally had no effect on the proliferative responses of tumor-bearing animals indicating that the suppression was not mediated through the cyclooxygenase pathway. We have also extended a previous observation in which UNF cells were found to be unresponsive to alloantigen stimulation. This suppression does not appear to be mediated through cyclooxygenase products as IND treatment does not enhance the UNF response although it does enhance the ADH response. These data indicate that a complex network of cyclooxygenase dependent and independent regulation exists in normal and tumor-bearing NBR rats.

Inhibitors of prostaglandin synthesis block the induction of staphylococcal enterotoxin B-activated T-suppressor cells

A variety of arachidonic acid metabolites possess the ability to modulate immune cell function. Various inhibitors of arachidonic acid metabolism were compared with regard to their effects on T-suppressor (Ts) cell function. Using staphylococcal enterotoxin B (SEB) to activate Lyt-2+ Ts cells, it was shown that indomethacin and 5,8,11,14-eicosatetraynoic acid (ETYA) inhibit the induction phase, but not the expression phase, of suppressor cell activity. Agents which inhibit thromboxane synthetase or lipoxygenase activities (imidazole, nordihydroguaiaretic acid, and pyrogallol) were not found to affect Ts cell induction. Since inhibitors of prostaglandin synthesis are thought to induce lower levels of cyclic adenosine monophosphate, an attempt to overcome the indomethacin inhibition of Ts cell induction by modulating cyclic adenosine monophosphate levels was made. It was found that theophylline and isoproterenol are not able to overcome the inhibition by indomethacin of Ts cell activity. These results strongly suggest that induction of Ts cells by SEB is dependent on the synthesis of products of the prostaglandin synthetase pathway.

Deficient T-cell mitogen response in murine experimental autoimmune myasthenia gravis: a defect in the adherent cell population

T-Lymphocyte number and functions are often reduced, while B-lymphocyte function is often increased in patients with autoimmune disorders. To study the mechanisms responsible for these T-cell malfunctions in autoimmunity we adapted the murine experimental autoimmune myasthenia gravis (EAMG) model. Splenocytes from C57BL/6 mice immunized with acetylcholine receptors (AChR) in complete Freund's adjuvant (CFA) produced approximately half the amount of concanavalin A (Con A)-induced interleukin 2 (IL-2) as did splenocytes of CFA-inoculated controls. Further, AChR plus CFA-immunized splenocytes showed a marked reduction in T-cell proliferative responses induced by Con A or phytohemagglutinin when compared with CFA-inoculated controls. By contrast, lipopolysaccharide-induced B-cell function is preserved. Deficient Con A splenic T-cell response is seen early after secondary inoculation with CFA or AChR in CFA. T-Cell recovery occurs in CFA-inoculated mice but not in AChR plus CFA-inoculated mice. Defective Con A splenic T-cell response seen early after secondary immunization with CFA or AChR in CFA is due to the presence of a defective splenic adherent cell population. Moreover, defective Con A splenic T-cell response seen after established autoimmunity to AChR in EAMG is also due to the presence of a defective splenic adherent cell population.

Potentiation of the canine lymphocyte blastogenic response by indomethacin

Cultivation of normal canine peripheral blood lymphocytes in the presence of indomethacin, a potent prostaglandin synthetase inhibitor, produced a consistent potentiation of their in vitro response to mitogenic stimulation as compared to cultures without indomethacin. The enhancing effect of indomethacin increased with decreasing concentrations of mitogens. Indomethacin had to be added to the cultures during the first four hours for the potentiating effect to be observed. These data suggest that prostaglandins may play an important role in the regulation of the dog's immune response.

Pharmacological modulation of suppressor cell activity in mice with disseminated histoplasmosis

Indomethacin and cyclophosphamide (CY) were used in an attempt to modify the suppressive effects of spleen cell populations from mice with disseminated histoplasmosis at 1 week of infection. In vitro addition of indomethacin did not alter the depressed plaque-forming cell response to sheep erythrocytes of normal spleen cells cocultured with unfractionated or nylon wool-fractionated spleen cells from infected mice. Likewise, indomethacin given intraperitoneally did not enhance the subnormal in vivo plaque-forming cell response of spleen cells from infected mice. Conversely, 20 mg of CY per kg given intraperitoneally 2 days before or 6 h after the inoculation with Histoplasma capsulatum partially reversed the suppression effected by splenic T cells (nylon wool passed) in vitro, whereas 50 mg of CY per kg given intraperitoneally 6 h after the injection of H. capsulatum ablated suppressor T cell activity in vitro; neither dosage of CY altered the suppression mediated by unseparated or nylon wool-adherent spleen cells. Furthermore, the administration of 50 mg of CY per kg failed to improve the depressed footpad responses of mice infected for 1 week to sheep erythrocytes in sheep erythrocyte-sensitized mice or to histoplasmin. These findings indicate that in experimental disseminated histoplasmosis, suppression effected by splenic T cells can be alleviated by CY; however, there is a persistent immunosuppressor mechanism(s) that cannot be counteracted by either indomethacin or CY.

The suppressive effect of peritoneal exudate macrophages on production of antibody to sheep erythrocytes in vitro

The effects of peritoneal exudate macrophages on antibody response to sheep erythrocytes (SRBC) were investigated in mice. Peritoneal exudate macrophages obtained from mice injected intraperitoneally with proteose peptone or Corynebacterium parvum 4 days earlier had stronger ability to phagocytize and degrade SRBC than normal resident macrophages. These macrophages suppressed antibody formation to SRBC in vitro as well as in vivo. This suppression was overridden by increasing the amount of SRBC and diminished completely by pretreatment of the macrophages with iodoacetate and partly by pretreatment with 2-deoxyglucose, both known to be inhibitors of phagocytosis, but not by addition of indomethacin to the in vitro culture. These results suggest that the suppression of antibody response by peritoneal exudate macrophages was due to the increased activity of these cells as scavenger cells, resulting in a reduced amount of effective antigenic stimulation, and that it was not mediated by a prostaglandin-dependent mechanism. The scavenger function of these macrophages may be due to Ia-negative macrophages.

Nonsteroid antiinflammatory drugs and tamoxifen for desmoid tumors and carcinoma of the stomach

The results of treatment of desmoid tumor patients with nonsteroid antiinflammatory drugs alone or in combination with tamoxifen are described. Tumor growth was inhibited in six of seven patients. Nonsteroid antiinflammatory drugs administered along with 5-fluorouracil and cyclophosphamide and other inhibitors of T-suppressor cells were used to treat nine patients with metastatic carcinoma of the stomach. Survival of these patients was extended so that after 12 months minimal follow-up the majority are well. A prospective controlled clinical trial is indicated.

Distribution of T-lymphocyte subsets in Hodgkin's disease characterized by monoclonal antibodies

Mononuclear-cell suspensions of lymph nodes, spleen and blood from 24 patients with active Hodgkin's disease (HD) were studied for possible imbalance of T and B lymphocytes, and T-lymphocyte subsets, using monospecific anti-T antibodies and other reagents. A profile showing T-cell predominance was demonstrated in lymph nodes and blood, with total T-cells ranging from 50-70% of the cell count. As defined by monoclonal antibodies, 70-85 of the latter comprised the "inducer" subclass, the remainder being "suppressor" cells. There were no essential differences between histologically involved and uninvolved lymph nodes from HD patients, though total T-cell proportions were lower in "normal lymph node" controls. The profiles of spleens electively removed, as part of pre-treatment staging procedures, showed reduced total T-cell numbers, whether these were involved with HD or not. These differences are accounted for principally by fewer T "inducer" cells (24%, in spleen, v. 54% in involved lymph nodes and 47% in "normal" control nodes). Possible explanations for these findings are discussed. Our results demonstrate similar profiles in histologically diseased and normal tissue, rather than any clear imbalance of T-cell proportions which might explain the profound disturbances of T-cell function frequently demonstrated in vivo and in vitro.

Augmentation of concanavalin A-induced immunosuppression by indomethacin

These studies show that, in BALB/C mice, when antibody synthesis against sheep red blood cells is suppressed by concanavalin A, treatment with indomethacin (4-8 mg/kg per os) will augment this suppression. Two other nonsteroidal anti-inflammatory drugs, flufenamic acid and meclofenamic acid (50 mg/kg), also have this effect, whereas phenylbutazone was inactive at this dose. The augmentation of concanavalin A-induced immunosuppression by indomethacin could not be demonstrated on the response to the T-independent antigen polyvinypyrrolidone. In contrast to indomethacin, which inhibits cyclooxygenase, neither nordihydroguaiaretic acid, an inhibitor of the lipoxygenase pathway, nor eicosa-5,8,11,14-tetraynoic acid, an inhibitor of both the cyclooxygenase and the lipoxygenase pathways, had this augmenting effect. Therefore, we do not have strong evidence that the absence of a prostaglandin is responsible for the effect of indomethacin. However, inhibition of the pathway leading to prostaglandin synthesis causes an increase in arachidonic acid metabolism via the lipoxygenase pathway. A product of this pathway, such as a leukotriene, may have immunosuppressive effects in this model. Evidence for the enhancement of a suppressor cell population is provided by an in vitro coculture assay. Cells treated with concanavalin A and indomethacin had more suppressive activity than cells treated with concanavalin A or indomethacin alone.

Exogenous additions of prostaglandins variably alter the blastogenic response of B and T lymphocytes from different mice lymphoid organs

Prostaglandins A1 and E2 enhance the 3H-thymidine (TdR) uptake in spleen cell cultures stimulated by two B-lymphocyte mitogens (E.coli lipopolysaccharide (LPS) and dextran sulfate (DXS) at concentrations ranging between 10(-8) and 10(-6) M. The same prostaglandin (PG) concentrations inhibited concanavalin A (Con A) activation of mouse spleen cells depleted or not from a glass-adherent prostaglandin-producing population of suppressor cells. After fractionation of spleen cells by nylon wool adherence, PGs diminished 3H-TdR uptake by nylon nonadherent (T-enriched) cells cultured in the presence of Con A and enhanced the activation of nylon adherent (B-enriched) cells by LPS. The proliferative response of thymic lymphocytes to Con A was drastically inhibited (70-95% by PGE2 10(-8)-10(-6) M. In cultures of purified bone marrow lymphocytes, PGE2 induced a dose-dependent inhibition of either LPS- or DXS-induced activation reaching a 30-40% inhibition at a PGE2 concentration of 10(-6) M. In the spleen, treatment of cells with anti-T sera and complement resulted in abrogation of PG-induced enhancement. Nevertheless, no inhibition of B-cell mitogenesis was observed in the presence of 10(-6) PGE2. From these results, it can be concluded that a different sensitivity of the proliferative response of lymphoid cells to exogenous PGs exists, depending on the subset (T or B) affected and/or the organ used as a source of these cells.

Involvement of prostaglandin E1 in delayed-type hypersensitivity suppression induced with live Mycobacterium bovis BCG

We previously showed the suppression of delayed-type hypersensitivity produced by live BCG-induced, plastic-adhering cells. The present study was undertaken to determine whether prostaglandin was one of the pharmacological mediators involved in this suppression. A high level of prostaglandin E1 was detected in the culture supernatant fluid of the live BCG-induced, adherent cells. Moreover, prostaglandin E1 could suppress the macrophage migration inhibition activity of peritoneal exudate cells from BCG cell wall-sensitized mice.

Prostaglandin E2-mediated enhancement of human plasma cell differentiation

Addition of prostaglandin E2 (PGE2) to blood mononuclear cell cultures containing pokeweed mitogen (PWM) enhances plasma cell (PC) differentiation measured by intracytoplasmic immunoglobulin 7 days later. T-cell mitogenesis to concanavalin A is inhibited using the same concentrations of PGE2. PGE2 failed to enhance the PC differentiation of lymphocytes from patients with systemic lupus erythematosus (SLE). Indomethacin, on the other hand, either had no effect or suppressed PC differentiation. The data is discussed in terms of the effect of PGE2 on human suppressor T-cell function.

Impaired autologous mixed lymphocyte reactivity in Hodgkin's disease

In patients with Hodgkin's disease, the impaired immune reactivity, especially of the thymus dependent system, is well established. This decreased immune response of the lymphocytes from the peripheral blood contrast to an increased lymphocytopoiesis in the the lymphatic organs with a hyperplasia of these tissues. We studied the reactivity of peripheral T lymphocytes from 20 patients with Hodgkin's disease and 26 healthy control persons against autologous and allogeneic non T cells respectively in the mixed lymphocyte culture (MLC). Our experiments show an extremely depressed autologous mixed lymphocyte reactivity (MLR) of T lymphocytes from patients with Hodgkin's disease compared to those from normal donors. In the allogeneic MLC, the proliferation of the patients' T cells was stronger than in the autologous MLC, but significant lower than the proliferation of normal T lymphocytes when stimulated by normal non T cells. Patients' non T cells stimulated T lymphocytes from healthy donors as well as non T lymphocytes from normals did. Finally, the autologous MLR of normal lymphocytes was significantly suppressed by 18 of 23 sera from Hodgkin's patients when these sera were substituted for normal AB serum in the cultures. These results demonstrate an impaired function of T lymphocytes from patients with Hodgkin's disease in the autologous MLC and the presence of one or more factors in their serum which inhibit the proliferation of normal lymphocytes in the autologous MLC. The role of suppressor cells and their factors will be discussed.

Suppression of murine T-cell mitogenesis by metabolic products of arachidonic acid

We examined the ability of arachidonic acid (AA) to inhibit mitogen stimulation of mouse splenic lymphocytes. Dose related suppression of [3H]-thymidine incorporation by cells stimulated with either phytohemagglutinin or concanavalin A occurred at concentrations of AA above 1 microgram/ml. AA-induced suppression required that AA be added to cultures within 6 hours of the addition of mitogen. Addition of AA at 24 hours resulted in diminished suppression, while delaying addition of AA until 48 hours had no effect on mitogen stimulation. Preincubation with AA did not alter mitogen stimulation when cells were washed free of AA. The addition of indomethacin or mefanamic acid to the cultures significantly reversed AA-induced suppression. Inhibitors of the lipoxygenase pathway or thromboxane synthesis had no effect, while an inhibitor of both thromboxane and prostacyclin synthesis partially prevented AA-induced suppression only at the highest concentration of AA. Removal of adherent cells resulted in a diminished capacity for AA to suppress mitogenesis and to stimulate PGE2 synthesis.

Abrogation of suppressor cell function by inhibitors of prostaglandin synthesis

The weekly intraperitoneal injection of rat erythrocytes into mice induces both a stable autoimmune state, as judged by the appearance of anti-mouse erythrocyte autoantibody and suppressor T cells capable of regulating this response; the latter being demonstrable only in a subsequent transfer system. This autoimmune response and the parallel anti-rat erythrocyte response were both insensitive to exogenous prostaglandin E2 (PGE2). The administration of prostaglandin synthetase inhibitors (indomethacin or aspirin) to mice undergoing immunization with rat erythrocytes had no effect on the anti-rat response, yet mildly exacerbated the onset of the autoimmune state and potently inhibited the generation of suppressor cells. Furthermore the administration of these drugs to recipients of suppressor cells virtually abrogated suppressor cell activity. These observations imply that both the generation and effector function of these suppressor cells may be modulated by prostaglandin synthetase inhibitors while at the same time T helper and B cell functions remain unimpaired.

Improvement of LIF release by mononuclear cell cultures by 24 h incubation before stimulation with ConA

By measuring granulocyte migration from clotted plasma droplets placed in Microtest II plates, leucocyte migration inhibitory factor (LIF) production by concanavalin A (ConA) stimulated mononuclear cell (MNC) cultures was tested. Moderate LIF production was observed when mononuclear cells were pulsed with ConA at 0 h, as compared with cells stimulated after 24 h culture which produced a significantly increased amount of LIF. Fresh adherent cells, when added to 24 h incubated MNC cultures before ConA stimulation, decreased LIF production, in contrast to in vitro irradiated or overnight cultured adherent cells. Indomethacin, when present during exposure to a ConA pulse of either MNC or of adherent cell-rich 24 h incubated MNC cultures, improved LIF activity significantly. This suggests that prostaglandin producing adherent cells, presumably cooperating with radiosensitive short-lived immunoregulatory T cells, are involved in suppression of LIF production by MNC cultures stimulated by ConA at 0 h.

Modulation by adherent cells and irradiation of in vitro LIF production by Con-A stimulated mononuclear cells

LIF activity production by ConA-stimulated mononuclear cells was tested by measuring granulocyte migration from clotted plasma droplets placed in Microtest II plates. 90 min. incubation of MNC cultures with ConA assured a significant LIF activity in the 24 h. culture supernatants. Removal of the adherent cells after ConA pulse exposure improved (p less than 0.05) LIF production. Enrichment with adherent cells of MNC cultures before ConA stimulation decreased LIF release. Irradiation (600 rad) of ConA stimulated MNC cultures, however, abrogated both phenomena induced by either removal or enrichment of the adherent cells. Indomethacin, when added during ConA pulse exposure to adherent cell rich MNC cultures, also increased LIF activity production. Both, PGE1 and supernatants of ConA-pulsed monocyte rich cultures had similar LIF impairing effects but the suppressive activity was abolished either by supernatants dialysis or by irradiation of stimulated MNC cultures.

Conversion of soluble immune response suppressor to macrophage-derived suppressor factor by peroxide

After incubation with soluble immune response suppressor (SIRS), a product of concanavalin A-activated Ly2+ T cells, macrophages release a factor that suppresses in vitro antibody responses, DNA synthetic responses to T-cell and B-cell mitogens, and division of several tumor cell lines. This factor, macrophage-derived suppressor factor (M phi-SF), is a protein with an apparent Mr of 55,000 that is inactivated by sulfhydryl compounds, certain amines, and iodide but not by other halides. In experiments reported here, conventional SIRS and SIRS produced by a cloned T-cell hybridoma were used to analyze formation of M phi-SF by SIRS-treated macrophages. Formation of M phi-SF was insensitive to inhibitors of protein and prostaglandin synthesis but was sensitive to catalase and cyanide, indicating that M phi-SF was not a newly synthesized product and that peroxide was important to its formation. As M phi-SF and SIRS have similar molecular weights and other properties, it is possible that M phi-SF is SIRS modified by peroxide. To test this possibility, SIRS was treated with H2O2 and M phi-SF activity was determined. H2O2 at 0.1-1 pM was sufficient to convert SIRS to M phi-SF; the reaction required approximately 15-20 min and was sensitive to cyanide. Several conventional peroxidase substrates inactivated M phi-SF produced by the SIRS-H2O2 reaction or by SIRS-treated macrophages. In addition, catalase and several of the compounds that directly inactivate M phi-SF also partially interfere with SIRS-mediated suppression of antibody responses. Collectively, these data suggest that SIRS-treated macrophages produce H2O2, which converts SIRS to M phi-SF, which has properties of an oxidized peroxidase-like protein and acts by oxidizing cellular components essential for cell division.

A study of immunoregulation of BALB/c mice by Echinococcus granulosus equinus during prolonged infection

Two models of intraperitoneal infection with E. granulosus equinus by protoscolices and by cyst passage in BALB/c mice were used to provide mesenteric lymph node cells for adoptive cell transfer into syngeneic recipient normal responder mice. The cell transfer inocula were shown to have depleted Thy-1 cells, but to be highly suppressive to the normal sheep erythrocyte response of the recipients. The nature of the depletion and non-specific suppression, and the infectious nature of the latter, are discussed in relation to other examples of mitogenic stimulation resulting in non-specific T cell suppressor activity. The functions of Ly-2,3+ cells, not only as suppressor, but as alloreactive cytotoxic cells, are discussed as a possible, autoimmune explanation for the longevity of the parasite within the mouse model, in contradistinction to the predictable early rejection of analogous xenografts.

Sympathetic innervation of murine thymus and spleen: a comparative histofluorescence study

Fluorescence microscopy of thymus and spleen from four strains of mice (C3H and ICR controls, AKR spontaneously leukemic and NZB autoimmune) revealed varicose noradrenergic (NE) fibers in perivascular and parenchymal regions of both organs. Thymic innervation was largely perivascular, but isolated islands and strings of free NE fibers were noted among thymic parenchymal cells. A morphological proximity between NE fibers in the thymus and mast cells was noted in all strains studied, but was exceptionally prominent in the NZB thymus. Perivascular plexuses within the splenic white pulp sent single NE fibers between the surrounding lymphocytes. Catecholamines and histamine have been shown to modulate lymphocyte development and activity in vitro. The present study provides morphological evidence that both NE and histamine are available to lymphocytes in thymus and spleen, and thus provides morphological evidence for neural modulation of immune activity in vivo.

Sympathetic innervation of murine thymus and spleen: evidence for a functional link between the nervous and immune systems

Sympathetic innervation was demonstrated in both perivascular and parenchymal regions of murine thymus and spleen. Catecholamine varicosities were associated with mast cells in these areas. The antibody response to sheep red blood cells of 7 week old mice that had been sympathectomized with six-hydroxydopamine (6OHDA) at birth was significantly elevated compared with saline treated controls. Alpha-methyl tyrosine (alpha-MT) and 6OHDA treatment of mice, producing a more complete sympathectomy, showed a significantly enhanced anti-SRBC response with respect to mice treated with alpha-MT or 6OHDA alone. Catecholamine levels in thymus, spleen, and adrenals of both experimental and control mice were measured using liquid chromatography with electrochemical detection (LCEC). The present study suggests that the sympathetic nervous system has a functional role in modulating the humoral immune response in vivo.

Selectivity in the effects of indomethacin on BCG-activated suppressor cell populations

Intravenous inoculation of BCG into C57 B1/6 mice activated natural suppressor cells in the bone marrow and induced suppressor cells in the spleen. The suppressor activity of these cell populations was determined by co-cultivating them with normal lymphocytes being immunized against allogeneic P815 cells in vitro. Six million cells from the spleen or bone marrow of BCG treated mice inhibited by more than 50% the alloimmunization of twenty million normal syngeneic lymphocytes. The suppressor cells were found in the nylon wool adherent population in spleen and in both the nylon wool adherent and non-adherent populations in bone marrow. Indomethacin, at a concentration of 10(-6)M, completely blocked the suppression generated by unfractionated spleen or adherent spleen from BCG treated mice. However, 10(-6)M and higher concentrations of indomethacin only partially blocked the suppression generated by unfractionated marrow or adherent marrow from BCG treated mice. The suppression generated by non-adherent marrow from BCG treated mice was completely insensitive to indomethacin.

"In vivo" effects of acetylsalicylic acid and two ether derived compounds on primary immune response and lymphoblastic transformation

A comparison was performed of acetylsalicylic acid and two ether derivatives (Benorilate and Eterilate) and indomethacin in order to ascertain the in vivo effects on the lymphoblastic transformation and the primary immune response in mice. The humoral response in Benorilate-and Eterilate-treated mice was 40-50% lower than that of the controls, whereas in acetylsalicylic acid-treated mice the response was only 25% inhibited. The number of immunoglobulin synthesizing cells was neither reduced by acetylsalicylic acid nor by its derivatives, although indomethacin treatments (used for comparative purposes) inhibited by 40% the number of direct plaque-forming cells on the days tested. Mitogen-induced proliferation of spleen lymphocytes was also inhibited in the treated mice; these inhibitions were negligible in the case of cells from acetylsalicylic acid-treated mice activated by concanavalin A and slight in cells from Benorilate-treated mice activated by bacterial lipopolysaccharide. When lymphocytes from drug-treated animals were further cultured in the presence of the same drug, a variable inhibition of mitogen-induced proliferation was observed. These different in vivo effects of acetylsalicylic acid and the two ether derivatives and indomethacin may be due to a distinct action on diverse lymphocyte subpopulations altering their cellular collaborative interactions or modifying the prostaglandin availability.