Effect of a single or repeated dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on T cell subpopulations in the Long-Evans rat.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) exposure results in adverse effects on the immune system of experimental animals. The purpose of this study was to compare the effects of a single and repeated dosing of TCDD on splenic T-cell subpopulations in Long Evans rats 9 days post-exposure to TCDD. A single dose (25 microg/kg body weight) of TCDD resulted in reduced body weight. The percentage and total number of CD4+ or CD8+ subsets and percentage of CD4+ or CD8+ cell cycling in the S and G2M phases were similar in the single dosed (25 microg/kg body weight) TCDD group compared with the vehicle control. A repeated dose (5 microg/kg/day for 5 days) of TCDD also resulted in a significant reduction in body weight. However, multiple doses of TCDD significantly decreased the percentage of the CD4+ subset and the percentage of CD4+ cells cycling in the S and G2M phases. No significant change occurred in the CD8+ cell subpopulation after single or multiple dosing with TCDD. These results demonstrated that repeated dosing of TCDD decreased the total percentage of CD4+ cells and the percentage of CD4+ cells cycling 9 days post-exposure, while an analogous single dose of TCDD failed to affect the CD4+ cell subpopulation. The difference in biological responses to a single versus 'equivalent' multiple (cumulative) dose of TCDD is discussed.
Huang
W
W
College of Veterinary Medicine, Oregon State University, Corvallis, 97331, USA.
Koller
L D
LD
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D018791:CD4 Lymphocyte Count / Q000187:drug effects; D018414:CD8-Positive T-Lymphocytes / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D005260:Female; D005434:Flow Cytometry; D016131:Lymphocyte Subsets / Q000187:drug effects*; D009929:Organ Size / Q000187:drug effects; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D051381:Rats; D020318:Rats, Long-Evans; D013154:Spleen / Q000166:cytology / Q000187:drug effects; D013601:T-Lymphocytes / Q000187:drug effects*
D000072317:Polychlorinated Dibenzodioxins