Single-dose topical exposure to the pyrethroid insecticide, permethrin in C57BL/6N mice: effects on thymus and spleen

Ameliorative effect of L-carnitine on lambda-cyhalothrin-induced anatomical and reproductive aberrations in albino mice

The objective of this research was to look at how the pesticide lambda-cyhalothrin (LCT) affected the liver, kidney, testis, and ovary of albino mice; and on morphological and skeletal features of the newborn of treated females. The study also aimed to test the ameliorative effects of L-carnitine (LC) against (LCT). Five sets of mice were created, Group 1 acted as the control, while Group 2 received a high dose of LCT, Group 3 received a high dose of LCT + LC, Group 4 received a low dose of LCT that was a residue of in khat (Qat), and Group 5 received a low dose of LCT + LC. The findings revealed that the treated groups' body weights were reduced significantly, whereas the absolute and relative weights of the liver in all groups were statistically decreased insignificantly. There were histopathological changes in the tissues in groups 2 and 4. While the tissues of the ovary and testis showed recovery in groups 3 and 5. When compared to the control group, the values of the seminiferous tubules parameters were statistically significant in the 3 and 5 groups. The newborn had a high dose of pesticides and showed some malformations in the skeleton. However, in group 3 the skeletal malformation was minimized and in-group 5 the skeleton malformations had completely disappeared. It could be concluded that LCT is highly harmful to mouse tissues and caused neonatal malformations, whereas LC has a marked protective effect against LCT.

Permethrin inhibits tube formation and viability of endothelial cells

BACKGROUND

Exposure to environmental chemicals has been linked with endothelial dysfunction, which is a leading cause of human diseases, including atherosclerosis. Permethrin is a frequently used synthetic pyrethroid insecticide for which longer exposure may cause toxicity in several types of tissues and the development of metabolic diseases, including atherosclerosis, obesity and diabetes. The present study was designed to evaluate the potential adverse effect of permethrin on the function and activity of human endothelial cells.

RESULTS

Permethrin was found to repress migration and tube formation by human umbilical vein endothelial cells (HUVECs) in a dose-dependent manner, as well as to significantly repress their viability after 24 and 48 h of treatment. Furthermore, increased reactive oxygen species (ROS) production was observed in cells treated with permethrin, and the permethrin-induced repression of cell viability was ROS-dependent. Permethrin did not influence apoptosis, necrosis or mitochondrial membrane potential in HUVECs.

CONCLUSION

The results of the present study suggest that permethrin represses angiogenesis and viability through ROS-dependent and cell growth-, apoptosis- and necrosis-independent means. © 2022 Society of Chemical Industry.

Agricultural Pesticides and Shingles Risk in a Prospective Cohort of Licensed Pesticide Applicators

BACKGROUND

Some pesticides are immunotoxic and have been associated with an increased risk of immune-mediated diseases. The risk of shingles, the clinical reactivation of varicella-zoster virus, increases with aging and immunosuppression; little is known about its associations with pesticides.

OBJECTIVE

We examined the use of agricultural pesticides in relation to incident shingles in a prospective cohort of licensed pesticide applicators.

METHODS

The study sample included 12,820 (97% male) farmers (enrolled in 1993-1997 in North Carolina and Iowa), who were followed for a median of 12 y (interquartile range: 11-13). Shingles was self-reported at enrollment and at follow-up. We evaluated ever-use of 48 agricultural pesticides reported at study enrollment in relation to shingles risk and considered exposure-response for intensity-weighted lifetime days (IWLDs) of use. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox proportional hazard models, adjusting for state, and allowing estimates to vary by median attained age (60 y).

RESULTS

Incident shingles was reported by 590 participants. Associations were positive (HRs>1.2) for ever- vs. never-use of eight insecticides, three fumigants, two fungicides, and five herbicides, and exposure-response trends were seen across increasing quartiles (Q3 and Q4>Q1) or tertiles (T3 and T2>T1) of IWLDs for four insecticides [permethrin (crops), coumaphos, malathion, and lindane], two fumigants (carbon tetrachloride/carbon disulfide and methyl bromide), and three herbicides [alachlor, trifluralin (<60 years of age) and 2,4-dichlorophenoxyacetic acid]. Shingles was not associated with total years or days per year mixed or applied any pesticides, but in older participants, shingles was associated with a history of a high pesticide exposure event [HR=1.89 (95% CI: 1.45, 2.45)].

CONCLUSIONS

Several specific pesticides were associated with increased risk of shingles in farmers, especially at higher levels of cumulative use. These novel findings, if replicated in other populations, could have broader implications for the potential effects of pesticides on vaccine efficacy and susceptibility to other infections. https://doi.org/10.1289/EHP7797.

Pyrethroid based pesticides - chemical and biological aspects

Human and animal welfare primarily depends on the availability of food and surrounding environment. Over a century and half, the quest to identify agents that can enhance food production and protection from vector borne diseases resulted in the identification and use of a variety of pesticides, of which the pyrethroid based ones emerged as the best choice. Pesticides while improved the quality of life, on the other hand caused enormous health risks. Because of their percolation into drinking water and food chain and usage in domestic settings, humans unintentionally get exposed to the pesticides on a daily basis. The health hazards of almost all known pesticides at a variety of doses and exposure times are reported. This review provides a comprehensive summation on the historical, epidemiological, chemical and biological (physiological, biochemical and molecular) aspects of pyrethroid based insecticides. An overview of the available knowledge suggests that the synthetic pyrethroids vary in their chemical and toxic nature and pose health hazards that range from simple nausea to cancers. Despite large number of reports, studies that focused on identifying the health hazards using doses that are equivalent or relevant to human exposure are lacking. It is high time such studies are conducted to provide concrete evidence on the hazards of consuming pesticide contaminated food. Policy decisions to decrease the residual levels of pesticides in agricultural products and also to encourage organic farming is suggested.

Permethrin exposure affects neurobehavior and cellular characterization in rats' brain

This study investigated the neurotoxic effects of permethrin on the cerebellum, hippocampus and prefrontal cortex of Wistar rats and its effects on some behavioral patterns. Fifteen adult male Wistar rats were grouped into three categories: Group A received 0.1 mL normal saline (control), and Groups B and C received mixed feed with 500 mg/kg and 1,000 mg/kg of 0.6% permethrin, respectively, for 14 days. The animals were assessed for memory, anxiety and exploratory locomotion and thereafter anesthetized and transcardially perfused with normal saline and 4% paraformaldehyde (PFA). Cerebellum, hippocampus and prefrontal cortex were excised from the whole brain and processed for tissue histology, histochemistry and immunohistochemistry. Oxidative status and lipid peroxidation were also assessed using catalase, glutathione peroxidase, superoxide dismutase and malondialdehyde as biomarkers. Results revealed dosedependent decrease in body weights but increase in cerebellar and prefrontal weights, depletion of endogenous antioxidant markers, cognitive deficits, reduced locomotor activities, degenerative changes in the microarchitecture at high doses and presence of chromatolytic cells at both low and high doses of permethrin. Astrocytes were activated while synaptophysin expression was downregulated. Permethrin causes dose-dependent neurotoxicity on the morphology, neurochemistry and oxidative status of different brain regions, and these could affect behavioral performance and other neurologic functions.

The effect of subacute poisoning with fenpropathrin on mice kidney function and the level of interleukin 1β and tumor necrosis factor α

Fenpropathrin (FEN) is a pyrethroid insecticide. Mammals can be exposed to these compounds with food and water as non-target organisms. Pyrethroids are classified into two types depending on chemical structure and neurotoxic effects. FEN has features of Type I and Type II pyrethroids. There is data that pyrethroids apart from neurotoxic properties, can be also nephrotoxic and immunotoxic. The aim of the study was to assess the influence of FEN on kidney function and concentration of proinflammatory cytokines: tumor necrosis factor alpha (TNFα) and interleukin 1 beta (IL-1β) in mice kidneys. Sixteen female mice were randomly divided into two groups: I—receiving saline and II—receiving FEN at the dose of 11.9 mg/kg ip for 28 consecutive days. On day 29 blood samples were obtained to measure serum creatinine concentration. The animals were killed, and kidneys were obtained in order to measure TNFα and interleukin IL-1β in mice kidneys with use of ELISA assay. The concentration of creatinine was (mean ± SD) in controls 0.2 ± 0.0 mg/dl in the group exposed to FEN 0.225 ± 0.046 mg/dl. TNFα concentration in the kidneys of controls was 6.154 ± 1.597 pg/ml and in the group intoxicated with FEN it was 6.318 ± 1.012 pg/ml. IL-1β concentration in the kidneys of controls was 4.67 ± 1.154 pg/ml while in the group intoxicated with FEN 27.983 ± 26.382 pg/ml (p < 0.05). In conclusion: FEN slightly affects kidney function and increases the concentration of proinflammatory IL-1β in mice kidneys, which supports the hypothesis about nephrotoxic and immunotoxic effect of this insecticide in non target organisms.

Current Research on the Safety of Pyrethroids Used as Insecticides

Pyrethroids are synthetic derivatives of natural pyrethrins extracted from Chrysanthemum cinerariaefolium. They are 2250 times more toxic to insects than to vertebrates due to insects' smaller size, lower body temperature and more sensitive sodium channels. In particular, three pyrethroid compounds, namely deltamethrin, permethrin, and alpha-cypermethrin, are commonly used as insecticides and are recommended for in-home insect control because they are considered to be relatively non-toxic to humans in all stages of life. However, recent data show that they are not completely harmless to human health as they may enter the body through skin contact, by inhalation and food or water, and absorption level depending on the type of food. Permethrin seems to have an adverse effect on fertility, the immune system, cardiovascular and hepatic metabolism as well as enzymatic activity. Deltamethrin induces inflammation, nephro- and hepatotoxicity and influences the activity of antioxidant enzymes in tissues. Alpha-cypermethrin may impair immunity and act to increase glucose and lipid levels in blood. The aim of the review is to provide comprehensive information on potential hazards associated to human exposure to deltamethrin, permethrin and alpha-cypermethrin. The results of presented studies prove that the insecticides must be used with great caution.

Prenatal and postnatal exposure to low levels of permethrin exerts reproductive effects in male mice

Permethrin, a pyrethroid chemical, is widely used as a pesticide because of its rapid insecticidal activity. Although permethrin is considered to exert very low toxicity on mammalian reproductive organs, the effects of early low-level and chronic exposure on adult spermatogenesis are unclear. We exposed mice to environmentally relevant concentrations of permethrin (0, 0.3, and 30ppm) in drinking water during prenatal and postnatal period and examined the effects on the testis in mice offspring when they reached maturity (12 weeks of age). Using methyl green-pyronin staining, we found an abnormal accumulation of RNA in the seminiferous epithelia of mice treated with permethrin; this accumulation may be derived from an enlargement of the residual body. Additionally, permethrin may cause a decline of Sertoli cell functions. Our findings demonstrate that low-level and chronic permethrin exposure during prenatal and postnatal period has distinct effects on male reproductive system in mice.

Urinary concentrations of pyrethroid metabolites and its association with lung function in a Canadian general population

OBJECTIVES

While there is increasing concern about the health impact of pyrethroid insecticides, little is known about their effect on lung function. In this cross-sectional study, urinary concentrations of pyrethroid (PYR) metabolites and their associations with lung function were examined among a Canadian general population using data from the Canadian Health Measures Survey (CHMS).

METHODS

Urinary concentrations of 5 pyrethroid metabolites (3-PBA, 4-F-3-PBA, cis-DCCA, trans-DCCA and cis-DBCA) were available for 5436 CHMS participants aged 6-79 years. Lung function parameters considered were forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC ratio and forced expiratory flow between 25% and 75% of FVC. Multiple linear regression analyses were used to examine associations between PYR concentrations and lung function in children (6-11 years), adolescents (12-19 years) and adults (20-79 years), respectively.

RESULTS

Almost all CHMS participants (99.8%) had PYR metabolites detectable in urine. In multiple linear regression analyses, 1 unit increase in log transformed urinary concentration (nmol/g creatinine) of total pyrethorid metabolites (ΣPYR) was associated with a 17.4 mL reduction in FEV1 (p=0.045) in children, a 37.1 mL reduction in FVC (p=0.05) in adolescents and a 0.3% (p=0.01) increase in FEV1/FVC ratio in adults.

CONCLUSIONS

These results show evidence of widespread exposures to pyrethroid insecticides among the Canadian general population. Pyrethroid exposures were associated with lower FEV1 in children, lower FVC in adolescents and relatively higher FEV1/FVC ratio in adults. Further research is necessary to confirm the potential effect of pyrethroid insecticides on lung function reported in this study.

Deltamethrin induced an apoptogenic signalling pathway in murine thymocytes : exploring the molecular mechanism

Deltamethrin (DLM) is a well-known pyrethroid insecticide; however, the immunotoxic effects of DLM on the mammalian system and its mechanism is still unclear. This study has been designed to first observe the binding affinity of DLM to immune cell receptors and its effects on the immune system. The docking score revealed that DLM has a strong binding affinity towards the CD4 and CD8 receptors. DLM induces apoptosis in murine thymocytes in a concentration-dependent manner. The ear\ly markers of apoptosis such as enhanced reactive oxygen species (ROS) and caspase-3 activation are evident as early as 1 h by 25 and 50 μM DLM. Glutathione (GSH) depletion has also been observed at 1 h by 50 μM DLM concentration. In cell-cycle studies using flow cytometry, the fraction of hypodiploid cells has gradually increased with all the concentrations of DLM at 18 h. The Annexin V binding assay measures the effect of DLM on apoptotic and necrotic cells. The apoptotic cells raised from 18.6% to 35.21% (10-50 μM DLM) at 18 h. N-acetyl cysteine (NAC) effectively reduced the percentage of apoptotic cells which is increased by DLM. In contrast, buthionine sulfoximine (BSO) caused an elevation in the percentage of apoptotic cells. These results demonstrate that caspase activation, ROS activation and GSH act as critical mediators in a DLM-induced apoptogenic signalling pathway in murine thymocytes. In the presence of caspase inhibitor, the percentage of apoptotic cells is partially decreased. Thus, there may be the possibility of some other caspase-independent pathways in DLM-induced apoptosis.

Effects of permethrin exposure on antioxidant enzymes and protein status in Mediterranean clams Ruditapes decussatus

The effects of permethrin (PER) on a panel of antoxidant enzymes; superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) and indices of protein oxidation status (carbonylation and free thiols) were determined in digestive gland and gills of the clam Ruditapes decussatus. Animals were exposed to 100 ppb PER for 2 days. These enzyme activities increased significantly in digestive gland (p<0.05) after PER treatment and oxidative modification of proteins was detected in both gill and digestive gland extracts using redox proteomics. PER exposure significantly reduced the amount of protein free thiol groups in digestive gland rather than in gill, when compared to controls. Conversely, digestive gland showed significantly higher levels of carbonylated proteins than gill after PER exposure. Some proteins were successfully identified by mass spectrometry of tryptic peptides. Our data suggest that digestive gland of R. decussatus can be used as a model tissue for investigating environmental risk of PER contamination.

Developmental exposure to diuron causes splenotoxicity in male Sprague-Dawley rat pups

This study investigated whether perinatal exposure to diuron [3-(3,4-dichlorophenyl)-1-1-dimethylurea] might exert adverse effects on rat lymphoid organs. Pregnant Sprague-Dawley (SD) rats were exposed to diuron at 500, 750 or 1250 ppm in the diet from gestational days (GD) 12-21 and during lactation. At postnatal day (PND) 42, male pups were euthanized and thymus, spleen, mesenteric lymph node and femur were collected for histopathological analysis. Food consumption and body weight gain were significantly reduced in dams exposed to 1250 ppm during gestation period. Also, Diuron at 750 and 1250 ppm produced: (1) increased relative spleen weight associated histologically with severe congestion in red pulp, (2) enhanced extramedullary hematopoiesis and hemosiderosis as well as (3) depletion of lymphoid follicles in white pulp. Flow cytometric analysis revealed a significant reduction in B lymphocytes (CD45RA+) in male pups but T lymphocytes (CD4+, CD8+ and CD4+/CD8+) were not markedly affected. Thus, data suggest that Diuron-induced maternal toxicity in dams exposed to high dose and perinatal exposure to this herbicide produced spleen toxicity as evidenced by a reduction in B lymphocyte number in male SD pups.

Cytotoxic effects of permethrin on mouse liver and spleen cells

This study analyzed the histopathological and histochemical effects of different dosages of permethrin on liver and spleen cells of mice, in order to evaluate the toxic potential of this substance and the possible impairments that this chemical causes in different tissues of nontarget organisms (laboratorial conditions). The results showed that permethrin caused severe alterations in the liver cells, reducing the size of the nuclei and causing hydropic degeneration of the hepatocytes, in addition to stimulating the proliferation of Kupffer cells, altered the amount of proteins, polysaccharides, lipids, and vacuoles in the cytoplasm of the hepatocytes and congested the hepatic capillaries. As for the spleen of the treated mice, no alterations were observed in the morphology in relation to the control group, what would suggest that the spleen would continue performing its functions, without suffering morphological alterations even in the presence of the toxic agent.

Diuron exposure induces systemic and organ-specific toxicity following acute and sub-chronic exposure in male Wistar rats

Diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] is a substitute urea herbicide widely used on agricultural crops with potential mutagenic, teratogenic, reproductive and carcinogenic effects. Nonetheless, its toxic potential on the immune system needs a detailed assessment. Thus, in order to evaluate the adverse effect of this herbicide on lymphohematopoietic organs and macrophage activity, male Wistar rats were orally treated with Diuron at 125, 1250 and 2500 ppm for 14, 28 or 90 days. General signs of toxicity were observed in Diuron-treated groups (1250 and 2500 ppm), including reduced food intake and body weight gain, as well as higher relative weights for spleen, kidneys and liver (28 and 90-day toxicity studies) and elevated serum levels of ALT, albumin, total protein, creatinine and urea (28-day toxicity study). Diuron exposure caused a severe depletion of splenic white pulp compartments and cellularity, followed by a decreased number of CD4(+) T lymphocytes, increased extramedullary hematopoiesis and deposition of hemosiderin in red pulp. Despite alteration in macrophage spreading, the macrophagic activity was not significantly affected by the herbicide. Under these experimental conditions, the results suggest that Diuron exerts systemic and target-organ toxicity, mainly at higher concentration.

Effects of the synthetic pyrethroid insecticide, permethrin, on two estuarine fish species

Limited toxicity data are available for estuarine and marine species and the widely used pyrethroid insecticide, permethrin. This study determined acute effects of permethrin on survival, lipid peroxidation, acetylcholinesterase activity, and splenocyte proliferation for two fish species found in South Carolina estuaries; juvenile red drum (Sciaenops ocellatus) and adult mummichog (Fundulus heteroclitus). Juvenile S. ocellatus were significantly more sensitive than adult F. heteroclitus to permethrin exposure, with a 96-h LC50 value of 8 μg/L determined for red drum compared to 23 μg/L for mummichog. Lipid peroxidation activity of the liver increased in permethrin-treated fish compared to control animals after 24 h and decreased after 96 h. Permethrin had no effect on acetylcholinesterase activity of the brain at the concentrations tested. Permethrin exposure significantly inhibited splenocyte proliferation, indicating an immunosuppressive effect. Most of the effects of permethrin on fish cellular stress enzymes and survival occurred at concentrations much higher than those typically measured in the environment. However, inhibition of splenocyte proliferation in juvenile red drum occurred at approximately twice that of measured permethrin concentrations in surface water. These findings may prove useful to the future management and regulation of pyrethroid insecticide use near estuarine habitats.

Immunotoxicity of pyrethroid metabolites in an in vitro model

Risk assessment of man-made chemicals such as pesticides are mainly focused on parent compounds, and relatively little is known about their metabolites, especially with regard to target organ damages such as immunotoxicity. In the present study, the immunotoxicity of five synthetic pyrethroids (SPs) and three common metabolites was evaluated using an in vitro model by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, cytoflow, and enzyme-linked immunosorbent assay (ELISA). Cell viability and apoptosis assays showed that both SPs and their metabolites possessed cytotoxicity to the monocytic cells. The aldehyde and acid derivatives were more effective than the other compounds at cytotoxicity, with inhibition of cell viability by 56.8 and 50.6% at 10⁻⁵ mol L⁻¹, and induction of 8.52 and 8.81% cell apoptosis, respectively. Exposure to SPs and their metabolites also led to changes in the secretion levels of tumor necrosis factor α (TNF α) and interleukins (ILs), and again the metabolites showed stronger effects than the parent compounds. The aldehyde derivative upregulated IL-12p70 level by 1.87-fold, and the alcohol and acid derivative increased the secretion of TNF α 5.88 and 7.96-fold, relative to the control group. In the in vitro model, the common metabolites of SPs clearly exerted greater immunotoxic effects to monocytes than the intact parent compounds. Results from the present study suggested the need for considering metabolites in achieving more comprehensive health risk assessment of man-made chemicals, including target organ toxicities such as immunotoxicity.

Effects of prometryne on apoptosis and necrosis in thymus, lymph node and spleen in mice

Prometryne is a methylthio-s-triazine herbicide. Significant traces are documented in environment, mainly waters, soil and plants used for nutrition. The aim of this study was to estimate prometryne immunotoxic properties through induction of apoptotic and/or necrotic changes in thymocytes, splenocytes and lymph node cells after repeated subchronical exposure. Three different doses of prometryne (185, 375, 555mgkg(-1)) were applied per os every 48h, over 28 days. Flow cytometry assay (annexinV-FITC and PI) was conducted to record apoptotic and necrotic damage. In the spleen significant changes in the percentage of apoptotic cells were not detected between treated and control groups respectively. In thymus and lymph node, within the lowest dose group (185mgkg(-)1), an increase in percentage of early apoptosis without any significant increase in necrosis was detected. Medium (375mgkg(-1)) as well as high dose triggered increase in late apoptosis in lymph node while in thymus; late apoptosis was increased only in animals exposed to the highest dose (555mgkg(-1)). The highest applied dose, in thymus and lymph node respectively, caused a general decrease in percentage of vital cells in favour of marked increase of percentages of all types of dying cells (apoptotic, late apoptotic/early necrotic and necrotic). Prometryne caused disbalance in major organs of immune system, markedly lymph nodes and thymus, by induction of early apoptotic changes in dose/time specific manner.

Permethrin may disrupt testosterone biosynthesis via mitochondrial membrane damage of Leydig cells in adult male mouse

Permethrin, a popular synthetic pyrethroid insecticide used to control noxious insects in agriculture, forestry, households, horticulture, and public health throughout the world, poses risks of environmental exposure. Here we evaluate the reproductive toxicity of cis-permethrin in adult male ICR mice that were orally administered cis-permethrin (0, 35, or 70 mg/kg d) for 6 wk. Caudal epididymal sperm count and sperm motility in the treated groups were statistically reduced in a dose-dependent manner. Testicular testosterone production and plasma testosterone concentration were significantly and dose-dependently decreased with an increase in LH, and a significant regression was observed between testosterone levels and cis-permethrin residues in individual mice testes after exposure. However, no significant changes were observed in body weight, reproductive organ absolute and relative weights, sperm morphology, and plasma FSH concentration after cis-permethrin treatment. Moreover, cis-permethrin exposure significantly diminished the testicular mitochondrial mRNA expression levels of peripheral benzodiazepine receptor (PBR), steroidogenic acute regulatory protein (StAR), and cytochrome P450 side-chain cleavage (P450scc) and enzyme and protein expression levels of StAR and P450scc. At the electron microscopic level, mitochondrial membrane damage was found in Leydig cells of the exposed mouse testis. Our results suggest that the insecticide permethrin may cause mitochondrial membrane impairment in Leydig cells and disrupt testosterone biosynthesis by diminishing the delivery of cholesterol into the mitochondria and decreasing the conversion of cholesterol to pregnenolone in the cells, thus reducing subsequent testosterone production.

Evaluation of the potential immunotoxicity of 3-monochloro-1,2-propanediol in Balb/c mice

3-Monochloro-1,2-propanediol (MCPD) is a well-known by-product of acid-hydrolyzed soy sauce during its manufacturing process. To evaluate the immunotoxicity of MCPD, we investigated its effect on the thymic subset, delayed-type hypersensitivity, mixed-lymphocyte reaction and peritoneal macrophage activity. MCPD was administered by gavage for 14 days at 0, 25, 50, and 100 mg/kg/day to female Balb/c mice. The thymic subsets and annexin-V positive cells in thymic cells were quantified by flow cytometry. Mixed-lymphocyte reaction, delayed-type hypersensitivity and peritoneal macrophage activity were assessed. The mixed-lymphocyte reaction and delayed-type hypersensitivity were not significantly changed. However, there were significant increases in the apoptosis of mice treated with high dose of MCPD compared to the vehicle control. A significant decrease in the CD4+CD8+ thymic subset of mice treated with high dose of MCPD was observed. The activity of peritoneal macrophage was significantly reduced in high dose group. These results indicate that MCPD could modulate the immune function in Balb/c mice.