Background: Trimellitic anhydride (TMA) is a low-molecular-weight compound capable of inducing occupational asthma in man. We have characterized the TMA-induced antibody responses in Brown-Norway rats (BNR) and evaluated the effects of treatment with the glucocorticoid betamethasone or with cyclosporin A (CsA) on this response.
Methods: Animals were sensitised by two intradermal injections of 0.1 ml TMA suspended in corn oil, and development of specific antibodies was assessed using ELISA.
Results: Both IgE and IgG anti-TMA antibodies started to rise between weeks 1 and 3 after immunisation, reached their highest levels 7 weeks after sensitisation with 3% of TMA and then started to decline. Betamethasone and CsA given orally over the time of sensitisation (8 days in total) inhibited the development of specific IgE and IgG anti-TMA antibodies. Betamethasone given 10-17 days after sensitisation attenuated the IgE and IgG antibody responses as well while treatment with CsA after sensitisation had no effect on the production of specific antibodies. Levels of total IgE and IgG were not affected except for a small decrease in total IgE using medium-dose betamethasone after sensitisation.
Conclusion: We conclude that TMA-sensitised BNR develop specific IgE and IgG anti-TMA antibodies, and that glucocorticoids and CsA attenuate this response.