Sensitivity of the SRBC PFC Assay vs. Eliza for Detection of Immunosuppression by TCDD and TCDD-like Congeners

The splenic antibody plaque-forming cell (PFC) assay to sheep red blood cells (SRBC) is considered to be one of the most sensitive assays for detection of immunosuppression, and traditionally has been used in immunotoxicity testing. However, an enzyme-linked immunosorbent assay (ELISA) (Temple et al., 1993), is gaining popularity as a more convenient and less expensive alternative. The PFC assay quantifies the number of anti-SRBC producing plasma cells in the spleen, while the ELISA measures SRBC-specific IgM antibody in the serum. This study was performed to compare the sensitivity of these two assays to detect immunosuppression by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and TCDD-like congeners. Two sets of 6-7 groups of female B6C3F1 mice (6-7 mice/group, 8-weeks-old) were given a single oral exposure to corn oil or different doses of TCDD or congeners. Seven days later, mice were immunized i.v. with SRBC. The first set of mice was evaluated by the PFC assay and the second by the ELISA, on day 4 or 5 post-immunization, respectively. The four TCDD congeners tested were: l,2,3,7,8-pentachlorodibenzo-ρ-dioxin (PeCDD), 1,2,3,4,7,-pentachlorodibenzofuran (4PeCDF), 3,3',4,4',5-pentachlorobiphenyl (PCB126) and 2,3',4,4',5-pentachlorobiphenyl (PCB118). The ED[50s] for TCDD and each congener were determined from the PFC and ELISA data. For all the chemicals tested the ED[50s] for the ELISA were lower than the ED[50s] for the PFC, with percent differences ranging from 33 to 84%. These results indicate that the ELISA is a more sensitive assay for detecting suppression of the SRBC-specific IgM response of dioxin-like chemicals in this rodent model and supports its use as a sensitive alternative to the PFC assay.Master of Science in Public Healt