In vivo and in vitro effects of 1,1-dimethylhydrazine on selected immune functions

Hormetic Dose-Response Relationships in Immunology: Occurrence, Quantitative Features of the Dose Response, Mechanistic Foundations, and Clinical Implications

This article provides an assessment of the occurrence of immune-system-related hormetic-like biphasic dose-response relationships. Such dose-response relationships are extensive, with over 90 different immune response-related endpoints reported, induced by over 70 endogenous agonists, over 100 drugs, and over 40 environmental contaminants. Such hormetic responses were reported in over 30 animal models, over a dozen mammalian and human cell lines. These findings demonstrate that immune-system-related hormetic-like biphasic dose-response relationships are common and highly generalizable according to model, endpoint, and chemical class. The quantitative features of the dose response are generally consistent with previously published examples of hormetic dose responses for other biological endpoints. These findings were generally recognized and explicitly discussed by the original authors, often with consideration given to possible mechanistic foundations as well as numerous clinical implications. Despite the recognition by individual authors of the hormetic nature of these observed responses, the overall widespread nature of immune-related hormetic responses has been only little appreciated, with a general lack of insight into the highly generalizable nature of this phenomenon as well as the complex regulatory networks affecting biological switching mechanisms that result in the hormetic responses.

Evaluation of murine lymphocyte membrane potential, intracellular free calcium, and interleukin-2 receptor expression upon exposure to 1,1-dimethylhydrazine

The effects of 1,1-dimethylhydrazine (UDMH) on several early events associated with lymphocyte activation were examined. The concentration of intracellular calcium ([Ca2+]i) and membrane potential of murine lymphocytes were found to be altered upon exposure to UDMH; [Ca2+]i was increased in murine thymocytes, while splenocytes exhibited membrane hyperpolarization. In addition, interleukin-2 receptor expression induced by in-vitro concanavalin A stimulation of murine splenocytes at 24 and 48 h in the presence of UDMH was not affected. UDMH may interfere with the ability of these two distinct lymphocyte populations to regulate normal ionic fluctuations, thus contributing to altered immune responsiveness.

Effect of 1,1-dimethylhydrazine (UDMH) on Corynebacterium parvum-associated immunosuppression in mice

These studies further investigate the immunoenhancement properties of UDMH by utilizing Corynebacterium parvum-induced immunosuppressed mice as well as evaluating activated macrophage production of reactive oxygen intermediates or their effects. Forty-eight hour Con A-induced lymphoblastogenic responses from splenocytes isolated from C. parvum and UDMH-treated Balb/C mice were significantly increased compared with C. parvum alone, although less than normal control mice (no treatment). In vitro bioassay of IL-2 production in cell culture supernatant isolated from these same treatment groups exhibited a pattern of stimulation similar to that of lymphocyte blastogenesis. In addition, UDMH did not interfere with H2O2-mediated suppression of either Con A- or LPS-induced lymphocyte blastogenesis and actually enhanced suppression of Con A-induced lymphocyte cultures at 25 micrograms/ml. We also report that production of superoxide anion from TPA-activated peritoneal macrophages exposed to various concentrations of UDMH in vitro was not affected. Although in vivo exposure to UDMH partially reversed C. parvum-induced immunosuppression in mice, the exact mechanism by which UDMH acts to reverse this immune suppression is not clear. UDMH does not appear to interfere with either activated peritoneal macrophage production of superoxide anion or H2O2-induced suppression of lymphocyte blastogenesis to elicit immune enhancement.

The in vitro and in vivo effects of 1,1-dimethylhydrazine (UDMH) on murine lymphocyte subsets and Ia antigen expression

1,1-Dimethylhydrazine or unsymmetrical dimethylhydrazine (UDMH) is a highly volatile and reactive compound used primarily as a liquid rocket propellant. Previous studies found UDMH to possess immunomodulatory activity similar to other hydrazine derivatives. Modulation of T lymphocyte subpopulations and Major Histocompatibility Complex Class II or Ia antigen were evaluated as possible mechanisms for this UDMH-induced immunomodulation. Murine lymphoid cell populations were examined by flow cytometry for changes in their cell surface marker percentages or relative number upon exposure to UDMH either in vitro or in vivo. The results show UDMH caused significant suppression of the T helper cell population derived from the thymus at the 75 mg/kg dose in vivo, but did not affect other lymphocyte subpopulations isolated from mesenteric lymph node, spleen or thymus at this or any other dose. In vivo exposure of mice at all doses of UDMH did not significantly alter expression of Ia antigens on adherent cell populations and expression of the Ia antigen following in vitro UDMH exposure was not affected as well. Results indicate that the immunomodulatory effects of UDMH are not mediated by phenotypic alteration of T lymphocyte subpopulations or Ia antigen.

In vitro modulation of macrophage functions by 1,1-dimethylhydrazine (UDMH): Possible mechanism for UDMH-induced immuno-enhancement

The in vitro effects of 1,1-dimethylhydrazine (UDMH) on prostaglandin E(2) (PGE(2)) synthesis, chemiluminescence, phagocytosis, microbicidal activity and chemotaxis in murine enriched-macrophage populations were evaluated. PGE(2) synthesis by resident peritoneal macrophages and chemiluminescence by activated macrophages were markedly suppressed in the presence of UDMH; phagocytosis and microbicidal activity were slightly to moderately suppressed, and chemotaxis was not affected. Two of these functions (PGE(2) synthesis and chemiluminescence) reflect macrophage immunoregulatory properties, and the UDMH-induced abrogation of these functions may be related to the previously reported immuno-enhancing effects of UDMH.

In vitro B-lymphocyte antigen priming against both non-immunogenic and immunogenic molecules requiring low amounts of antigen and applicable in hybridoma technology

A method to efficiently antigen-prime B-lymphocytes with low amounts (less than 1 microgram/10(8) cells) of either immunogenic or non-immunogenic molecules is described. Keyhole limpet hemocyanin (KLH) and histone were used as prototypes for strongly immunogenic and for phylogenetically conserved non-immunogenic epitopes, respectively. Several modifications of previously reported methods were applied to the system and resulted in the requirement of antigen amounts sufficiently low to be obtainable by elution of proteins from electrophoretic gels. Antigen priming against highly purified antigen preparations is thereby feasible even when purified material cannot be obtained by conventional biochemical procedures. The amount of T- and B-lymphocytes and interleukin-2 production was estimated under various conditions during the priming procedure, and those optimal for generation of a high number of antigen-specific B-lymphocytes determined. In vitro antigen-primed B-lymphocytes were immortalized by conventional hybridoma technology. By fusion of lymphoid cells with myeloma cells at each day during the antigen-priming period, the optimal day of fusion to generate antigen-specific hybridomas was determined. Further, in 12 experiments with different antigens, 11 monoclonal antibodies to histones H3 and H4, two to the murine glucose transporter, 17 to trinitrophenyl-sheep red blood cells, and 20 to KLH were obtained. All specific hybridomas produced IgMs, as the antigen-priming period could not be extended for more than 9-10 days, whereafter a rapid decay in B-lymphocytes occurred.

Immunization in vitro and production of monoclonal antibodies specific to insoluble and weakly immunogenic proteins

A procedure is described for immunizing in vitro and stimulating proliferation of specific B-cell lymphocytes. The method is applicable to production of monoclonal antibodies against proteins that are soluble only in denaturing solvents. An induction period is described in which antigen is presented to the B-cell population in the absence of serum. Also, antigen is coupled to mitogenic silica, which allows the effective presentation of both soluble and insoluble antigens. The results indicate hybridomas can be obtained that secrete IgMs directed against highly conserved or weakly immunogenic antigens.