RESUMO
OBJECTIVE: Evaluation of the dynamics of all-trans retinoic acid receptor binding properties in mouse spleen nuclear extracts during a primary immune response against beta-galactosidase. METHODS: Female BALB/c mice, aged between 5 and 6 weeks were immunized intradermally into the shaved back (4 spots each) with 100 microg beta-galactosidase in 100 microl sterile phosphate buffered saline (pH 7.2) and blood was taken by tail bleeding on days 0 (preimmune serum), 4 and 6. Production of antibody in serum and the detection of cytokines (IL-4, IFN-gamma) from proliferation supernatants were determined by ELISA. Antigen-specific proliferation assay of isolated spleen cells was based on [3H]-thymidine incorporation measured in a liquid scintillation counter. Both, the maximal binding capacity (Bmax) and the affinity (Ka) of all-trans retinoic acid nuclear receptors (RAR) were evaluated according to Brtko (1994). RESULTS AND CONCLUSIONS: Injection of beta-galactosidase induced the first detectable antibody responses on day 4 (IgM) and on day 6 (IgG). These points of time, reflecting the early and the mature immune response served to measure the antigen-specific proliferation and production of IL-4 and IFN-gamma in the supernatants of the proliferation cultures as well as all-trans retinoic acid receptor (RAR) binding characteristics in spleen nuclear proteins. The RAR Bmax was significantly (P<0.05) decreased only at the time of the first specific IgG antibody production. CONCLUSIONS: The data obtained indicate the involvement of RAR in the late phase of an in vivo immune response.
