IMMUNOGLOBULIN-E PRODUCTION IN MICE BY MEANS OF CONTACT SENSITIZATIONWITH A SIMPLE CHEMICAL, HAPTEN

Production of IgE caused by repeated topical application of 2,4-dinitr ofluorobenzene (DNFB) to the ears of BALB/c mice was investigated. Ear thickness increased in proportion to the number of applications. Ecze matous changes of the skin included marked infiltration of neutrophils , eosinophils, and monocytes and hypertrophy of the epidermis. Ear thi ckness due to inflammation reached a maximum 24 hours after the second , third, fourth, and fifth applications. The strong expression of inte rferon-gamma and IL-2 messenger RNA (mRNA) in the skin lesions indicat ed the participation of Th1 type helper T cells in the delayed-type hy persensitivity reaction. After the fifth application, the mice showed an immediate cutaneous reaction in addition to the delayed-type hypers ensitivity reaction. The immediate reaction appeared within 1 hour of application, Hapten-specific IgE also was detected in serum from the m ice, and the expression of germline and productive C epsilon mRNA was detected in cervical lymph nodes, whereas productive C epsilon mRNA wa s detected in the spleen. These results indicate that five topical app lications of DNFB to the ear produce local eczematous dermatitis and i ncrease serum hapten-specific IgE level in mice, Eczematous dermatitis is mainly caused by Th1 type T cells, and IgE production is mediated by Th2 type T cells in the cervical lymph nodes. In addition, IgE clas s switching occurs in the cervical nodes and IgE production occurs in both Lymph nodes and spleen.