T cells reactive to keratinocyte antigens are generated during induction of contact hypersensitivity in mice. A model for autoeczematization in humans?

BACKGROUND: The role of keratinocytes (KC) in contact hypersensitivity (CH) has been examined more with respect to cytokine secretion and tolerance induction and less as a source of antigenic proteins to which chemical haptens can conjugate. OBJECTIVE: To determine whether KC-derived proteins can serve as antigenic carriers for haptens such as dinitrofluorobenzene (DNFB). METHODS: We examined the capacity of draining lymph node cells from BALB/c mice sensitized to DNFB to proliferate in response to hapten or to hapten-conjugated protein extracts derived from a KC line (DNP-Pam KC extract). Using limiting dilution microculture of these lymph node cells, we established DNP-specific T cell clones as well as DNP-Pam KC extract-reactive T cell clones. We also examined the proliferative responses of the DNP-Pam KC extract-reactive clones and of lymph node cells from mice sensitized to different haptens. RESULTS: Lymph node cells from DNFB-sensitized mice proliferated well to hapten or to DNP-Pam KC extract. Six la(d)-restricted, alphabeta TCR-bearing, CD4+ clones were established: 4 proliferated specifically to soluble hapten (DNBS), whereas 2 proliferated in response to DNP-Pam KC extract. Surprisingly, the DNP-Pam KC extract-reactive clones proliferated as well to Pam KC extract without hapten. Lymph node cells from hapten-sensitized mice not only proliferated specifically in response to the hapten to which they were sensitized, but also proliferated to Pam KC extract without hapten. CONCLUSIONS: T cell clones generated during the induction of (CH) in mice include those reactive to hapten as well as those reactive to KC antigens independent of hapten. Analogous mechanisms in humans might account for autoreactive events such as id reactions associated with CH and angry back syndrome during patch testing.

Contact sensitization induces proliferation of heterogeneous populations of hapten-specific T cells.

To characterize the T cells that are activated during the induction of contact hypersensitivity (CH), two sets of studies were conducted: 1) dinitrophenol (DNP)-specific proliferative responses of T cells in draining lymph nodes of BALB/c mice sensitized epicutaneously to dinitrofluorobenzene (DNFB) were examined, and 2) from these lymph node cells, DNP-specific T cells were cloned by limiting dilution microculture and analyzed by FACS for surface markers, by RT-PCR, HT2 bioassay and ELISA for cytokine expression at mRNA and protein levels respectively, and by proliferation assay for cytokine and antigen-presenting cell (APC) requirements. Our results show that alpha beta TCR-bearing T cells of both the CD4+ and CD8+ subtypes from lymph nodes of DNFB-skin-painted mice proliferate specifically to dinitrobenzene sulfonate (DNBS) in vitro. Four DNP-specific, CD4+ T-cell clones were characterized: clone 5S4 secreted IL-4 and required Il-4 for optimal growth; clone 5S10 secreted IL-2 and required IL-2 for optimal growth; clone 5S2 secreted IL-4 but required IL-2 for optimal growth; and clone 5S8 secreted IL-2 predominantly at 5 months, but switched to production of IL-4 at 7 months. All four clones secreted IL-10, and proliferated to DNBS when Langerhans cell (LC)-enriched epidermal cells were used as APC. These findings indicate that heterogeneous populations of DNP-specific T cells are activated in draining lymph nodes during the induction of CH to DNFB in BALB/c mice.