Gene expression alterations in immune system pathways in the thymus after exposure to immunosuppressive chemicals.

Background: Dysregulation of positive and negative selection, antigen presentation, or apoptosis in the thymus can lead to immunosuppression or autoimmunity. Diethylstilbestrol (DES), dexamethasone (DEX), cyclophosphamide (CPS), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) are immunosuppressive chemicals that induce similar immunotoxic effects in the thymus, however, the mechanism of toxicity is purported to be different for each compound.

Objectives: We hypothesized that genomic analysis of thymus after chemical-induced atrophy would yield transcriptional profiles that suggest pathways of toxicity associated with reduced function.

The sheep erythrocyte T-dependent antibody response (TDAR).

The sheep erythrocyte T-dependent antibody Response (TDAR) evaluates the ability of animals sensitized in vivo to produce primary IgM antibodies to sheep erythrocytes (sRBC). The assay enumerates the number of antigen specific IgM antibody producing cells in the spleen. When exposure to the test material takes place in vivo, as does sensitization, the actual quantification of the number of antibody producing cells occurs ex vivo.