Functional heterogeneity of human T cell clones from atopic and non-atopic donors.

Several distinct T helper (TH) subsets have been identified, based on the cytokines secreted. Recently, it has been demonstrated that these subsets can regulate the isotype of humoral responses. To investigate the possible differences in TH subsets between atopic donors which have elevated serum IgE and donors with normal serum IgE, we examined series of human TH cell clones. A total of 31 and 22 CD4+ T cell clones from the atopic and non-atopic donors, respectively, were characterized for the ability to help for IgE synthesis in vitro. T cell clones generated with allergen AgE from the atopic donor were autoreactive and all induced IgE synthesis. Tetanus toxoid-specific (TT) and phytohaemagglutinin clones were generated from both donors. There was significant heterogeneity between the T cells isolated with different stimuli from the same atopic donor. Also, there was a significant difference in the number of T cells generated from the atopic versus the non-atopic donor which helped for IgE, although there was no significant difference between the total number of T cells able to help for immunoglobulin synthesis of other isotypes. Most importantly, there was a higher frequency of clones able to support IgE synthesis between TT-specific T cell clones generated from the atopic versus the non-atopic donor. These results suggest that there are changes in subsets of TH cells specific for microbial antigens as well as allergens in atopics, which may have important implications for the aetiology of atopic disease.