Suppression Of Plaque-forming Cell Response Research Articles

Halogenated aromatic hydrocarbon-induced suppression of the plaque-forming cell response in B6C3F1 splenocytes cultured with allogenic mouse serum: Ah receptor structure activity relationships

The immunsuppressive effects of halogenated aromatic hydrocarbons (HAHs) were investigated in B6C3F1 female mice and in mouse splenocytes cultured with allogenic mouse serum using the Mishell-Dutton model for in vitro immunization to trinitrophenyl-lipopolysaccharide (TNP-LPS). Exposure to 2,3,7,8-tetrachlorodibenzo- P-dioxin (TCDD), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), 1,2,3,7,8-PeCDF, 1,3,6,8-tetrachlorodibenzofuran (TCDF), 3,3′,4,4′,5-pentachlorobiphenyl (pentaCB), or 3,3′,4,4′,5,5′-hexaCB resulted in a dose-dependent suppression of the splenic plaque-forming cell (PFC) response both in vivo and in vitro. The effective dose required to decrease 50% (ED 50) of the response to 2,3,7,8-TCDD, 2,3,4,7,8-PeCDF, 1,2,3,7,8-PeCDF, 1,3,6,8-TCDF, 3,3′,4,4′,5-pentaCB, or 3,3′,4,4′,5,5′-hexaCB in vivo was 14.1, 5.5, 1695, 34800, 21, and 19 nmol/kg, respectively, and in vitro was 7.0, 10.6, 149, 2325, 9.1 and 9.1 nM, respectively. There was an excellent rank order and linear correlation between the in vivo versus in vitro activities for these HAHs ( r < 0.99) and the relative immunosuppressive potencies of these compounds paralleled their binding affinities for the aryl hydrocarbon (Ah) receptor. These results show that splenocytes cultured with allogenic mouse serum is an Ah-responsive in vitro assay which can be used for quantitating the immunosup-pressive effects of HAHS.

Quaternary naltrexone: its immunomodulatory activity and interaction with brain delta and kappa opioid receptors

To investigate the role of brain opioid receptors in immune reactions, quaternary naltrexone (QNtx), a nonselective opioid antagonist which does not cross the brain-blood barrier, was tested for its immunomodulatory activity and ability to antagonize immunological changes produced by centrally applied delta-receptor agonist methionine-enkephalin (Met-Enk) and kappa-opioid receptor agonist MR 2034. Plaque-forming cell (PFC) response served as an immunological model. For this purpose, different groups of Wistar rats were centrally (intracerebroventricularly, i.c.v.) and peripherally (intraperitoneally, i.p., or subcutaneously, s.c.) treated with different doses of Met-Enk, MR 2034 and QNtx. Centrally injected Met-Enk and MR 2034 induced a dose-dependent potentiation and suppression of PFC response, respectively. Small amounts of i.c.v. given QNtx produced a dose-dependent increase in the number of PFC, whereas peripherally administered antagonist potentiated immune response in a dose-independent manner. A dose of 10 μg/kg of QNtx given i.c.v. completely abolished the immunopotentiation by Met-Enk. However, a large dose of 5 mg/kg of QNtx given s.c., did not affect the Met-Enk-induced immunoenhancement. Immunosuppression produced by i.c.v. injected MR 2034 was totally abrogated by prior i.c.v. application of QNtx, but partially blocked by s.c. administration of the antagonist. These results suggest that: (a) QNtx itself potentiates the humoral immune response when applied centrally in small doses (1 to 10 μg/kg) or peripherally in relativelly large doses (0.2 to 5 mg/kg), (b) immunopotentiation and immunosuppression induced by i.c.v. given Met-Enk and MR 2034, respectively, appears to be preferentially mediated through brain opioid receptors, (c) QNtx antagonizes the immunomodulating activities of Met-Enk and MR 2034, and (d) peripheral opioid systems may also contribute to the immunomodulation evoked by centrally administered kappa-receptor agonist MR 2034. As a whole, this study provides evidence for the involvement of the central opioid system in mechanisms underlying the immune responsiveness.

Species and strain comparisons of immunosuppression by 2-methoxyethanol and 2-methoxyacetic acid

2-Methoxyethanol (ME) and its principal metabolite 2-methoxyacetic acid (MAA) have been shown in our laboratory to be immunosuppressive in male Fischer 344 rats. In this study several strains of 12-week-old female rats and mice were used to compare the immunosuppressive activity of equimolar concentrations of ME and MAA on the trinitrophenyl-lipopolysaccharide (TNP-LPS) antibody plaque-forming cell (PFC) response, which we previously demonstrated to be a sensitive end point. Female inbred Lewis, Fischer 344 and Wistar/Furth, and outbred Sprague-Dawley rats were dosed by gavage with either ME or MAA at dosages of 0.33 to 2.64 mmol/kg/day for 10 consecutive days. Female inbred C3H and C57BL/6J, hybrid B6C3F 1, and outbred CD-1 mice were similarly dosed with equimolar dosages of 0.66 to 5.28 mmol/kg/day ME or MAA. All animals were immunized on day 9 of dosing and PFC responses evaluated 3 days later. Suppression of the PFC response was observed in all strains of rats at 2.64 mmol/kg/day ME or MAA. Lewis and Wistar/Furth rats were found to be the most sensitive strains with suppression at levels as low as 0.66 mmol/kg/day ME or MAA. While ME and MAA dosing resulted in suppression of the TNP PFC response in all the rat strains tested, such treatment did not suppress this PFC response in any of the mouse strains examined. These results indicate that under the conditions of this study rats, but not mice, are immunosuppressed by ME and MAA exposure, and that the susceptibility to immunosuppression differs among rat strains.

Locus ceruleus and immunity. I. Suppression of plaque-forming cell response and antibody production in rats with lesioned locus ceruleus.

Earlier research had demonstrated that lesions placed in different brain structures may alter the immune responsiveness. Norepinephrine is one of neurotransmitters which plays a role in immune reactions, and the locus ceruleus represents the largest group of norepinephrine-containing neurons in the brain. The present study concerns, therefore, the relationship between the locus ceruleus and humoral immune reactions. For this purpose, rats with electrolytically induced lesions in locus ceruleus were used in the study. Locus ceruleus-lesioned animals showed a decreased ability to produce hemolysin-releasing cells, hemagglutinins, and antibodies to bovine serum albumin. In brain-lesioned rats, thymus tended to the smaller in size, and there was a depletion of CD4+ helper/inducer lymphocyte population in the peripheral blood.

Immunosuppression induced by attenuated Salmonella. Reversal by IL-4.

We previously demonstrated that an aroA- strain of Salmonella typhimurium, which provides excellent protection against virulent Salmonella challenge, also rendered immunized mice unable to mount in vivo and in vitro antibody responses to heterologous Ag. Coculture studies using transwell plates indicated that suppression was mediated by soluble factors. The suppressive cells were identified as belonging to the monocytic linkage. Macrophage precursors as well as mature adherent macrophages mediated the observed suppression. In the present study, the mechanism of immunosuppression was investigated. Suppression was found to be genetically nonrestricted as spleen cells from immunized C3HeB/FeJ mice (H-2k) suppressed the anti-SRBC plaque-forming cell (PFC) responses of normal spleen cells from two MHC noncompatible mouse strains, BALB/c (H-2d) and C57BL/6 (H-2b). Time course experiments demonstrated that the addition of spleen cells from immunized mice to normal splenocytes as late as day 4 of a 5-day assay was still markedly suppressive. Furthermore, suppression of the PFC responses was accompanied by a profound inhibition of the capacity of immune splenocytes to produce IL-2 in response to in vitro stimulation by Con A. Coculture studies showed that immune spleen cells were able to suppress IL-2 production by normal splenocytes in a dose-dependent fashion. However, the suppressed PFC responses of immune spleen cells could not be reversed by the exogenous addition of up to 200 U/ml of IL-2, suggesting that immune splenocytes are also defective in their ability to respond to IL-2. In marked contrast, suppression of PFC responses was reduced by more than 50% by the addition of as little as 1 U/ml of IL-4 and was completely abrogated when 5 U/ml of IL-4 were added to in vitro cultures of spleen cells from immunized mice. The antisuppressive action of IL-4 appeared to be via its inhibitory effect on activated macrophages. The implications of the above findings are discussed.

Suppression of immune responses to sheep erythrocytes by the lymphokine soluble immune response suppressor (SIRS) in vivo.

Soluble immune response suppressor (SIRS) is a protein produced by activated suppressor T lymphocytes which inhibits division by tumor cells and plaque-forming cell (PFC) responses in vitro. Although this lymphokine has been fairly well characterized in vitro, little is known about its effects in vivo. Purified murine SIRS, 10(3) to 10(4) U injected i.p., suppressed murine PFC responses to sheep erythrocytes (SRBC) in vivo. Suppression occurred when SIRS was injected into mice 5 days before assay, and also occurred when SIRS activated with 10(-6) M H2O2 was injected 24 hr before assay. These kinetics are similar to those observed in tissue culture, where suppression of PFC responses requires the addition of SIRS 4 to 5 days before assay unless SIRS is activated to SIRSox by H2O2. Levamisole, an inhibitor of SIRS-mediated suppression in vitro, also blocked suppression by SIRS in vivo. Delayed-type hypersensitivity reaction to footpad injection of SRBC was also inhibited by SIRS. Suppression of PFC responses by recombinant immune interferon (IFN-gamma), which activates lymphocytes to produce SIRS in vitro, was blocked by injection of levamisole or monoclonal anti-SIRS antibodies. These results show that SIRS suppresses immune responses in vivo, and suggest that suppression of PFC responses by IFN-gamma may be largely mediated by SIRS. These findings indicate that SIRS could contribute to the development of suppressed immunity in vivo.

Reversal of murine alveolar macrophage-mediated suppression of plaque-forming cell response by sodium periodate

Murine alveolar macrophages (AM) have been shown to suppress the in vitro plaque-forming cell (PFC) response of spleen cells previously primed with sheep erythrocytes (SRBC) in a dose-dependent manner. Mild oxidation of cell membranes on viable AM with sodium periodate resulted in total abrogation of AM-mediated suppression of the PFC response, while periodate treatment of spleen cells resulted only in partial reduction of the suppression. Pretreatment of AM with sodium periodate followed by addition of the aldehyde blocking agent, hydroxylamine, resulted in restoration of the PFC-suppressing activity of AM. Periodate treatment of AM also resulted in significantly increased macrophage-T-cell binding and cluster formation. These observations suggest that the generation of aldehyde moieties on AM membrane sialoglycoconjugates promotes positive macrophage-lymphocyte interactions, resulting in abrogation of AM-mediated suppression of the PFC response.

Human natural killer-like activity against mouse spleen cells.

Unstimulated human peripheral lymphocytes were cytotoxic for normal mouse spleen cells and suppressed the in vitro antibody plaque-forming cell (PFC) response of these cells to sheep red blood cells and dinitrophenylated Ficoll. The cells in the lymphocyte population that were responsible for the immunosuppression had properties of natural killer (NK) or NK-like cells in that they were: (a) non-E-rosetting, (b) nonadherent, (c) unaffected by treatment with anti-human immunoglobulin plus complement, (d) cytotoxic against an established human NK target, K562 leukemic cells, and (e) partially inactivated by mitomycin C. Addition of the human NK-like cells to mouse spleen cell cultures at the time of antigen addition and at an effector cell to target cell ratio as low as 0.67:1 resulted in 85 to 96% suppression of the PFC response. Addition of NK-like cells to cultures 18 h before harvesting in 5-day cultures required higher concentrations and ratios (2.7:1) of effector to target cells to significantly suppress the PFC response. The data suggest that human NK-like activity in suppression of the mouse PFC response is due to killing of the targets. The mouse spleen cell PFC system represents a potential model for assessment of human NK activity that is quite dramatic in its effect and can be used in addition to the well known 51Cr-release assay. Also, since the mouse spleen cell is a normal cell, it provides a model in the PFC system for studying the mechanism of NK regulation of normal cellular function. An additional finding of this study was the observation that E-rosetting T cells significantly enhanced the mouse PFC response. Thus, human peripheral lymphocytes contain discrete cellular population that either enhance or suppress the mouse PFC response.

Hapten-specific T cell responses to 4-hydroxy-3-nitrophenyl acetyl. VII. Idiotype-specific suppression of plaque-forming cell responses.

The ability of suppressor cells induced by the intravenous administration of 4-hydro-3-nitrophenyl acetyl (NP)-modified syngeneic cells to reduce an idiotypic B cell response was studied in both an in vivo and an in vitro system. Idiotype-positive B cells were assayed by the ability of guinea pig anti-idiotypic antiserum to specifically inhibit idiotype-positive plaque formation. It was found that up to 57% of the PFC response in vivo and 100% of the PFC response in vitro was inhibitable with antiidiotypic antiserum. The expression of these idiotype-positive B cells could be suppressed by the transfer of spleen cells form mice treated 7 d previously with NP coupled syngeneic cels. T cells are both required and sufficient for the transfer of idiotype specific suppression. The induction of these idiotype-specific T suppressor cells directly with antigen suggests that recognition of unique determinants on cell surfaces is important for regulation of lymphoid cell interactions. The role of idiotype-specific suppressor cells in the network of lymphoid interactions is discussed.

Influence of anterior hypothalamic lesions on circulating antibody titers in the rat.

Influence of anterior hypothalamic lesions on circulating antibody titers in the rat.