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Time course of specific antibody production following topical skin exposure to dry trimellitic anhydride (TMA) powder.

Zhang-XD; Millecchia-LL; Kommineni-C; Lewis-DM; Siegel-PD
Toxicologist 2001 Mar; 60(1):174
TMA is a low molecular weight chemical used in the solid form as a fine powder in industry. Workers have been reported to develop asthma after TMA exposure and specific anti- TMA IgE has been found in these workers. Although inhalation has been considered the major route of exposure leading to sensitization, the importance of dermal exposure in allergic sensitization is not known. The consequences of dermal exposure to dry TMA powder in a Brown Norway rat (BNR) model are explored in the present study. Dry TMA powder was applied to an area of the back which the hair had been carefully clipped, and occluded with surgical tape overnight. One group received a single application of TMA (20 mg) on day 0 and a second group received repeated exposure to 20 mg of TMA applied once per week for 4 weeks. Sera were taken on days 0, 7,14,21,28 and 35, and analyzed for TMA specific IgE and IgG by ELISA. Skin from the application areas was taken for histopathological and immunohistochemical examination. Specific IgE and IgG could be detected in the sera of rats from both groups on day 14. Antibody levels increased and persisted through day 35 in both groups. Specific antibodies were not found in either unexposed or trimellitic acid exposed controls groups. Histopathology of TMA exposed skin was normal with no evidence of inflammation or tissue destruction. Immunohistochemical staining using autologous anti TMA IgG demonstrated strong reaction of the TMA only at the stratum cornea. These data suggest that in BNR, TMA powder exposure to the skin produces persistent immunological sensitization, without adjuvants and at doses that do not produce inflammation at the application site. This persistent antibody response was demonstrated even after a single dermal exposure suggesting that the antigen(s) formed by TMA in the tissues is not readily cleared horn the body.
Antibody-response; Skin-exposure; Bronchial-asthma; Workers; Worker-health; Work-environment; Occupational-exposure; Sensitization; Inhalation-studies; Laboratory-animals; Animals; Animal-studies; Models; Histopathology; Immunological-tests; Skin-tests; Antigens
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The Toxicologist. Society of Toxicology 40th Annual Meeting, March 25-29, 2001, San Francisco, California