Small Chemicals, Bioactivation, and the Immune System – A Fragile Balance of i-Tox and Benefits?

Immunotoxicity effects of carbaryl in vivo and in vitro

Carbaryl is a pesticide for controlling pests in agricultural industry. To determine of immunotoxicity effects of carbaryl, rats were exposure with carbaryl for 28 days. The lymphoid organ weight, lymphocyte proliferation, IL-2, IFN-γ, IL-4, IL-10, IL-1β and TNF-α cytokines level were measured, respectively. Exposure with carbaryl significantly reduced both thymus and spleen weight and also suppressed lymphocyte proliferation. In addition, carbaryl significantly decreased IL-2, IFN-γ, IL-1β and TNF-α and also increased IL-4, IL-10 cytokines. These findings suggest that exposure to carbaryl can induce immunotoxicity effects on lymphoid organ weight, suppresses the functions of lymphocyte and macrophage, Th2 polarization in Th1/Th2 balance by reducing of IFN-γ and increasing of IL-4 and IL-10 cytokines. Therefore, carbaryl can contribute to the development of allergic, autoimmune, cancer or infection diseases through immunotoxicity effects and unbalancing of Th1/Th2 immune response however, further study is necessary.

Cytokine patterns in greenhouse workers occupationally exposed to α-cypermethrin: an observational study

The immunotoxicity of the synthetic pyrethroid α-cypermethrin (αCYP) was assessed in 30 occupationally exposed greenhouse workers and 30 non-exposed controls by comparing plasma levels of IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p70, TNF-α, TNF-β and INF-γ. Urinary 3-phenoxybenzoic acid was used as an exposure biomarker. Exposed workers showed neither clinical signs of immunosuppression nor alterations in total leukocytes or leukocyte subpopulations, whereas significant differences (p<0.05) were found for IL-12p70 and highly significant differences (p<0.001) for INF-γ, IL-2 and IL-8, which are involved in antitumor immunity and response to infection. Proinflammatory cytokines IL-2, IL-8, IL-12p70 and IFN-γ play a significant role against infection and cancer. We report the first data on the ability of αCYP to reduce proinflammatory cytokine levels in an exposed healthy human population. Findings support the hypothesis that pyrethroid exposure may reduce host defenses against infection and cancer, particularly in subjects with impaired immune capacity.

Immunomodulation and hormonal disruption without compromised disease resistance in perfluorooctanoic acid (PFOA) exposed Japanese quail

This study evaluated the impact of oral perfluorooctanoic acid (PFOA) on Japanese quail at concentrations found in American and Belgian workers at PFOA manufacturing facilities. Three arms of the immune system were tested; T cell, B cell, and innate immunity. After 6 weeks exposure, quail were challenged with E. coli infection to test the ultimate measure of immunotoxicity, disease resistance. The T cell response was lower in the high exposure groups. Antibody mediated, and innate immune responses were not different. Growth rate was higher, whereas thyroid hormone levels were lower in PFOA-exposed birds. Morbidity/mortality from disease challenge was not different among the control and PFOA-exposed groups, and no overt PFOA toxicity was observed pre-disease challenge. Although PFOA at 'worst case scenario' levels caused T cell immunosuppression, this did not translate into increased disease susceptibility, demonstrating that immunotoxicity testing must be interpreted with caution since disease resistance is the ultimate concern.

Pesticide induced immunotoxicity in humans: a comprehensive review of the existing evidence

The immune system can be the target of many chemicals, with potentially severe adverse effects on the host's health. In Western countries pesticides, together with new and modified patterns of exposure to chemicals, have been implicated in the increasing prevalence of diseases associated with alterations of the immune response, such as hypersensitivity reactions, certain autoimmune diseases and cancers. Xenobiotics may initiate, facilitate or exacerbate pathological immune processes, resulting in immunotoxicity by induction of mutations in genes coding for immunoregulatory factors, modifying immune tolerance and activation pathways. The purpose of this article is to update the evidence of pesticide immunotoxicity. Even if experimental data as well as sporadic human studies indicate that some pesticides can affect the immune system, overall, existing epidemiological studies are inadequate to raise conclusions on the immunotoxic risk associated to pesticide exposure. The available studies on the effects of pesticides on human immune system have several limitations including poor indication on exposure levels, multiple chemical exposures, heterogeneity of the approach, and difficulty in giving a prognostic significance to the slight changes often observed. Further studies are necessary, and they should be preferably carried out through comparison of pre and post-exposure findings in the same group of subjects with a matched control group. Attempt should be made to define the prognostic significance of slight changes often observed. Animal and in vitro studies are also important and necessary to scientifically support epidemiological evidences on pesticide-induced immunotoxicity.

Immunotoxicity and disease resistance in Japanese quail (Corturnix coturnix japonica) exposed to malathion

The purpose of this study was to evaluate the impact of malathion on the immune system of wild birds, using Japanese quail (Coturnix coturnix japonica) as a model. Quail were exposed to malathion in drinking water at environmentally realistic concentrations (0 ppm, 1 ppm, and 10 ppm). In the fifth week, several arms of the immune response were tested using the T-cell based phytohemagglutinin (PHA) skin test, the B-cell mediated antibody response, and the chemiluminescence assay measuring innate immunity. After the sixth week of malathion exposure, quail were challenged with E. coli O2. The bursa of Fabricius and the spleen were assessed for histopathology. No clinical signs of malathion toxicity were observed. Morbidity or mortality subsequent to E. coli exposure tended (P = 0.08) to be higher in the high exposure group (50.0%) compared to the control (22.2%) group. There was no difference in the innate immune response in the malathion exposed birds, however, humoral immunity was suppressed (P = 0.03) with the higher malathion exposure. Histopathological evaluation revealed an immunosuppressive effect of malathion on the bursa of Fabricius; bursal atrophy, decreased B-cell density and increased apoptosis in the medulla, and increased connective tissue thickness of the follicular epithelium. Antibody suppression was correlated with bursal changes and peripheral blood lymphocyte count, the organ and cells involved in antibody production. Following the same pattern as other immunotoxicity tests, the PHA T-cell proliferative response also tended to be suppressed in the high exposure group. This study provides evidence that subchronic, moderate malathion exposure is immunotoxic to quail and that testing integrated, functional immunity using an infectious challenge is a better predictor of immunotoxicity than individual responses to immunotoxicity tests. The secondary antibody response, circulating lymphocyte populations, and bursal histopathology were the most sensitive indicators of immune status, as these predicted decreased disease resistance with malathion exposure.

Subchronic lead exposure, immunotoxicology and increased disease resistance in Japanese quail (Corturnix coturnix japonica)

The present study investigated the effects of lead (Pb) on immune responses in quail (Coturnix coturnix japonica) and the pathological impact of exposure to an infectious agent (E. coli O2). Fifty-four, 4-week-old quail were exposed to lead acetate in drinking water at 5 or 50 ppm. All birds were vaccinated with Newcastle Vaccine (NDV) during the third week of contaminant (Pb) exposure. In the fourth week, several arms of the immune response were tested using the T cell based phytohemagglutinin (PHA) skin test, the B cell mediated antibody response to NVD, and the chemiluminescence assay measuring innate immunity. Immunohistochemistry (IHC) was used to determine the expression of toll like receptor-3 (TLR-3) in the bursa of Fabricius. In the fifth week, quail were challenged with 200 μL of E. coli O2 (1×10(4) colony forming units (CFU)/mL). No clinical signs of Pb toxicity were observed. Morbidity/mortality subsequent to E. coli exposure was lowest in the high exposure group (27.8%) compared to low exposure (44.4%) and control (55.5%) groups. There was no difference in the T-cell-mediated PHA response, primary or secondary immune response or the innate response in Pb exposed groups; however, bursal TLR-3 increased (p<0.05) with higher Pb exposure. No evidence supported that subchronic Pb exposure was immunotoxic to quail at 5 or 50 ppm in drinking water. In contrast, our results provide evidence of a hormetic effect, with Pb exposed birds having lower morbidity and better survival than controls. Subchronic Pb exposure may be immunostimulatory rather than suppressive as predicted in earlier studies based on testing individual immune parameters.