Phenotypic Characterization of Human CD4+ Regulatory T Cells Obtained from Cutaneous Dinitrochlorobenzene-Induced Delayed Type Hypersensitivity Reactions

In this study, we describe the generation and characterization of cloned human CD4 + T lymphocyte populations that have infiltrated into cutaneous, 2,4-dinitrochlorobenzene-induced delayed type hypersensitivity reactions in healthy human subjects. It is shown that, in addition to T helper type 1 clones, elevated numbers of regulatory T clones, producing high levels of interleukin-10 and interleukin-5, but no measurable interleukin-4, were isolated from delayed type hypersensitivity reactions in four of six donors. A subsequent challenge with 2,4-dinitrochlorobenzene of two donors from whom only few interleukin-10-producing T cell clones had been generated after primary challenge, resulted in a decrease in the frequency of T helper type 1 clones and a strong increase in the number of interleukin-10-producing T helper type 2 and regulatory T clones. Culture supernatants from the latter cells, activated with anti-CD3 and anti-CD28 monoclonal antibody, inhibited alloantigen-mediated T cell proliferation which was, partly dependent on interleukin-10, and independent of transforming growth factor-β. In addition, dendritic cells generated in vitro in the presence of these culture supernatants were impaired in their ability to induce alloantigen-induced proliferative responses. Differential expression of transcripts for the T1/ST2 molecule enabled a phenotypic distinction between resting regulatory T cells and T helper type 2 cells, but not between regulatory T cells and T helper type 1 cells. This experimental model provides a useful tool to isolate human inflammatory and anti-inflammatory T cell subpopulations and, furthermore, enables the study of the kinetics of their appearance into delayed type hypersensitivity reactions.