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Results of a cyclosporin A ringstudy
H B Richter-Reichhelm1, A E Schulte
1Bundesinstitut für gesundheitlichen Verbraucherschutz und Veterinärmedizin, Berlin, Germany.
Toxicology
|October 13, 1998
Summary
An extended toxicity study detected immune system effects from cyclosporin A (CsA) at lower doses than general toxicity. This enhanced methodology shows potential for identifying immunotoxicity earlier in chemical testing.
Area of Science:
- Toxicology
- Immunology
- Pharmacology
Background:
- Standard toxicity testing may not detect subtle immunotoxic effects.
- Cyclosporin A (CsA) is a known immunosuppressant, making it a suitable model compound.
Purpose of the Study:
- To evaluate if extended toxicity testing can identify immune system effects below general toxicity.
- To assess the immunomodulatory potential of CsA in a repeated dose study.
Main Methods:
- A 28-day oral repeated dose toxicity study in rats (OECD guideline 407) using CsA at 1, 5, and 25 mg/kg.
- Included standard toxicity assessments plus extended histopathology, organ weights, and comprehensive immune functional tests.
- Immune parameters evaluated: immunoglobulin levels, plaque-forming assay, flow cytometry, macrophage and NK cell activity, and lymphocyte proliferation.
Main Results:
- CsA induced general toxicity (reduced body weight gain, kidney calcification) at higher doses.
- Specific morphological alterations in lymphoid tissues were observed in mid- and high-dose groups.
- Immune function alterations were detected down to the low-dose group, indicating sensitivity of the extended methods.
Conclusions:
- Extended subacute toxicity studies, incorporating detailed immunotoxicity assessments, can detect adverse immune effects at doses below general systemic toxicity.
- This approach holds promise for updating repeated dose toxicity guidelines to better assess chemical immunotoxicity.
- Further studies with immunostimulatory compounds are planned to validate the methodology.