5,7-dichloro-4-(4-fluorophenoxy)quinoline;quinoxyfen (ISO)

Immunotoxicity

Description of key information

28-Day Rat Diet NOAEL: 20 mg/kg/day; no humoral immune response. EPA OPPTS 870.7800; Reliability = 1

Key value for chemical safety assessment

Effect on immunotoxicity: via oral route

Link to relevant study records

Reference

Endpoint:

immunotoxicity: short-term oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.7800

Deviations:

no

GLP compliance:

yes

Limit test:

no

Specific details on test material used for the study:

- Substance ID: TSN 100097
- Name of substance: XDE-795
- Lot number: DECO-97-152-1
- Purity: 97.3%

Species:

rat

Strain:

other: F344/DuCrl

Sex:

male

Route of administration:

oral: feed

Vehicle:

other: diet

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

at least 28 days

Frequency of treatment:

daily

Dose / conc.:

20 mg/kg bw/day

Dose / conc.:

100 mg/kg bw/day

Dose / conc.:

250 mg/kg bw/day

No. of animals per sex per dose:

10

Control animals:

yes, plain diet

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

Clinical observations consisted of one animal in the 20 mg/kg/day group with periocular soiling noted on test day 28. This observation was considered spurious and unrelated to treatment due to the isolated occurrence and lack of dose response.

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weights of animals in the 250 mg/kg/day group were decreased throughout the duration of the study ranging from 4-8.8% and were statistically identified on test days 11 and 15. Bodyweight gains were also decreased throughout the study ranging from 6.6-26.2%. At study termination the body weights and body weight gains were decreased 7.2 and 15.3%, respectively. These decreases in body weight and body weight gain were interpreted to be treatment-related and were attributed to lower feed consumption. There were no treatment-related differences in the body weights or body weight gains of animals in the 20 and 100 mg/kg/day groups when compared to control animals.
There was a treatment-related decrease (7.2 %) in final body weight of males given 250 mg/kg/day when compared to the respective controls. The lower final body weight was associated with a 15.3% decrease in final body weight gain and a treatment-related decrease in feed consumption at this dose level throughout the study.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Feed consumption of animals in the 250 mg/kg/day group was decreased throughout the study ranging from 5.4-12.9% and was statistically identified on test day intervals 1-4 and 22-29. This difference correlated with decreases in body weight and body weight gains. There were no treatment-related differences in feed consumption of animals in the 20 and 100 mg/kg/day groups when compared to their respective controls.
Rats were given diets targeted to provide 0, 20, 100, or 250 mg/kg/day, which corresponded to actual time-weighted average doses of 0, 22.4, 113, or 276 mg/kg/day, respectively.

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

There were no treatment-related changes in any of the hematologic parameters.

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Males given 100 or 250 mg/kg/day had increases in relative liver weights of 7.8 and 12.1%, respectively, relative to control animals, which were statistically identified and interpreted to be treatment related. Rats given 250 mg/kg/day also had a statistically significant increase in relative kidney weights of 7.5% relative to control animals.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

There were no treatment-related gross pathologic observations with the exception of the tail lesions where gross pathological observations consisted of scabbing and/or infarct of the distal portion of the tail. All gross pathologic observations were considered to be spontaneous alterations, unassociated with exposure.

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

The observed tail lesions were interpreted to be due to technical errors and/or complications during tail vein injections. The tail lesion was inadvertently not collected. There were no treatment-related histopathologic observations. All observations were considered to be spontaneous or iatrogenic alterations unassociated with exposure to test substance.

Other functional activity assays:

effects observed, non-treatment-related

Description (incidence and severity):

The immunotoxic potential of the test substance was assessed through the evaluation of the primary antibody response to sheep red blood cells (SRBC) using an enzyme-linked immunosorbant assay (ELISA) approach that measured the concentration of serum anti- SRBC IgM. Analysis of the data revealed no statistically significant differences between the three doses of test substance and the vehicle control. A non-statistically significant 25% decrease in the anti-SRBC IgM response was noted in the high-dose group (250 mg/kg/day), however, this was without dose response and coincided with considerable general toxicity indicative of a maximum tolerated dose, including decreased body weights (7.2%) and body weight gains (15.3%) and significant increases in relative liver and kidney weights. Therefore, this decrease was considered to be secondary to the effects observed for this dose group. Furthermore, the responses for the high-dose animals were within the full range of responses observed for the individual control animals.
Based on these results, test substance did not exhibit evidence of immunotoxicity as it did not result in a treatment-related decrease in the primary immune response to SRBCs in male rats.

Key result

Dose descriptor:

NOEL

Effect level:

20 mg/kg bw/day

Based on:

test mat.

Sex:

male

Basis for effect level:

organ weights and organ / body weight ratios

Conclusions:

NOEL (rat): 20 mg/kg/day (based on organ weight)
The test substance did not exhibit evidence of immunotoxicity as it did not result in a treatment-related decrease in the primary immune response to SRBCs in male rats

Executive summary:

Ten male F344/DuCrl rats per group were given test diets formulated to supply 0, 20, 100, or 250 milligrams test substance per kilogram body weight per day (mg/kg/day) for at least 28 days to evaluate the potential for immunotoxicity following US EPA OPPTS 870.7800. Actual time-weighted average doses were 0, 22.4, 113, or 276 mg/kg/day, respectively. An additional group of ten male F344/DuCrl rats exposed to 0 mg/kg/day were included to serve as positive immunosuppressive controls and received intraperitoneal doses of 20 mg/kg cyclophosphamide on study days 24-28. Parameters evaluated were daily cage-side observations, weekly detailed clinical observations, body weights, feed consumption, hematology, selected organ weights, serum anti-SRBC IgM concentrations, gross examinations, and histopathologic examinations of selected tissues.

Subsequent to immunization with SRBCs via intravenous tail vein injections, five rats (four controls and one low-dose animal) developed darkening or scabbing of the distal portion of the tail. The lesions were histologically characterized as focally extensive areas of inflammation of the epidermis, dermis, and panniculus and were considered to be due to inadvertent technical errors and/or complications during tail vein injections. These lesions were found to impact various endpoints within the study, which may have confounded the data interpretation, therefore, all five animals were excluded from body weight, body weight gain, feed consumption, organ weight, hematology, and ELISA analyses.

Body weights of animals in the 250 mg/kg/day group showed a treatment-related decrease throughout the duration of the study ranging from 4-8.8% and were statistically identified on test days 11 and 15. Bodyweight gains for this group also showed a treatment-related decrease throughout the study ranging from 6.6-26.2%. At study termination the body weights and body weight gains for this group were decreased 7.2 and 15.3%, respectively. These decreases were concomitant with decreases in feed consumption which ranged from 5.4–12.9% throughout the study and were statistically identified on test day intervals 1-4 and 22-29. The effects on feed consumption and body weight observed in the 250 mg/kg/day group were considered treatment related and are consistent with effects reported in a previous 28-day dietary study in F344 rats. There were no treatment-related differences in the body weights, body weight gains or feed consumption for animals in the 20 and 100 mg/kg/day groups when compared to controls.

Rats given 100 or 250 mg/kg/day had statistically identified increases in relative liver weights of 7.8 and 12.1%, respectively, relative to control animals. Rats given 250 mg/kg/day also had a statistical increase in relative kidney weights of 7.5% relative to control animals. The effects on both the liver and kidney were considered treatment related and are consistent with effects reported in a previous 90-day dietary study in F344 rats. Rats given 250 mg/kg/day also had a statistically identified lower absolute spleen weights which were interpreted to be a secondary response reflective of a lower body weight at this dose level.

There were no additional treatment-related effects on any of the evaluated parameters including clinical signs, hematology, organ weights or gross observations.

The immunotoxic potential of test substance was assessed through the evaluation of the primary antibody response to sheep red blood cells (SRBC). Analysis of the data revealed no statistically significant differences between the three doses of test substance and the vehicle control. A non-statistically significant 25% decrease in the anti-SRBC IgM response was noted in the high dose group (250 mg/kg/day), however, this was without dose response and coincided with considerable general toxicity indicative of a maximum tolerated dose, including decreased body weights (7.2%) and body weight gains (15.3%) and significant increases in relative liver and kidney weights. Therefore, this decrease is considered to be secondary to the toxicity observed for this dose group. Furthermore, the responses for the high dose animals were within the full range of responses observed for the individual control animals. The positive control cyclophosphamide produced a statistically significant and greater than 99% reduction in the anti-SRBC IgM response.

Based on the results of this study, test substance did not exhibit evidence of immunotoxicity as it did not result in a treatment related decrease in the primary immune response to SRBCs in male rats. The overall no-observed-effect level (NOEL) for this study was the targeted concentration of 20 mg/kg/day test substance based on a statistically significant increase in relative liver weight in the 100 mg/kg/day dose group.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Effect on immunotoxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Effect on immunotoxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Ten male F344/DuCrl rats per group were given test diets formulated to supply 0, 20, 100, or 250 mg/kg/day for at least 28 days to evaluate the potential for immunotoxicity. An additional group of ten male F344/DuCrl rats exposed to 0 mg/kg/day were included to serve as positive immunosuppressive controls and received intraperitoneal doses of 20 mg/kg cyclophosphamide on study days 24-28. Parameters evaluated were daily cage-side observations, weekly detailed clinical observations, body weights, feed consumption, hematology, selected organ weights, serum anti-SRBC IgM concentrations, gross examinations, and histopathologic examinations of selected tissues. Subsequent to immunization with SRBCs via intravenous tail vein injections, five rats (four controls and one low-dose animal) developed darkening or scabbing of the distal portion of the tail. The lesions were histologically characterized as focally extensive areas of inflammation of the epidermis, dermis, and panniculus and were considered to be due to inadvertent technical errors and/or complications during tail vein injections. These lesions were found to impact various endpoints within the study, which may have confounded the data interpretation, therefore, all five animals were excluded from body weight, body weight gain, feed consumption, organ weight, hematology, and ELISA analyses. Body weights of animals in the 250 mg/kg/day group showed a treatment-related decrease throughout the duration of the study ranging from 4-8.8% and were statistically identified on test days 11 and 15. Bodyweight gains for this group also showed a treatment-related decrease throughout the study ranging from 6.6-26.2%. At study termination, the body weights and body weight gains for this group were decreased 7.2 and 15.3%, respectively. These decreases were concomitant with decreases in feed consumption which ranged from 5.4–12.9% throughout the study and were statistically identified on test day intervals 1-4 and 22-29. The effects on feed consumption and body weight observed in the 250 mg/kg/day group were considered treatment related and are consistent with effects reported in a previous 28-day dietary study in F344 rats. There were no treatment-related differences in the body weights, body weight gains or feed consumption for animals in the 20 and 100 mg/kg/day groups when compared to controls. Rats given 100 or 250 mg/kg/day had statistically identified increases in relative liver weights of 7.8 and 12.1%, respectively, relative to control animals. Rats given 250 mg/kg/day also had a statistical increase in relative kidney weights of 7.5% relative to control animals. The effects on both the liver and kidney were considered treatment related and are consistent with effects reported in a previous 90-day dietary study in F344 rats. Rats given 250 mg/kg/day also had a statistically identified lower absolute spleen weights which were interpreted to be a secondary response reflective of a lower body weight at this dose level. There were no additional treatment-related effects on any of the evaluated parameters including clinical signs, hematology, organ weights or gross observations.

The immunotoxic potential of test substance was assessed through the evaluation of the primary antibody response to sheep red blood cells (SRBC). Analysis of the data revealed no statistically significant differences between the three doses of test substance and the vehicle control. A non-statistically significant 25% decrease in the anti-SRBC IgM response was noted in the high dose group (250 mg/kg/day), however, this was without dose response and coincided with considerable general toxicity indicative of a maximum tolerated dose, including decreased body weights (7.2%) and body weight gains (15.3%) and significant increases in relative liver and kidney weights. Therefore, this decrease is considered to be secondary to the toxicity observed for this dose group. Furthermore, the responses for the high dose animals were within the full range of responses observed for the individual control animals. The positive control cyclophosphamide produced a statistically significant and greater than 99% reduction in the anti-SRBC IgM response. Based on the results of this study, test substance did not exhibit evidence of immunotoxicity as it did not result in a treatment related decrease in the primary immune response to SRBCs in male rats. The overall no-observed-effect level (NOEL) for this study was the targeted concentration of 20 mg/kg/day test substance based on a statistically significant increase in relative liver weight in the 100 mg/kg/day dose group.

Justification for classification or non-classification

The test substance did not produce a humoral response in rats in a 28-day immunotoxicity study. Therefore, the substance does not need to be classified for mutagenicity according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.