A Novel Non-Contact Communication Between Human Keratinocytes And T Cells: Exosomes Derived From Keratinocytes Support Superantigen-Induced Proliferation Of Resting T Cells

It is widely accepted that keratinocytes act as non-professional antigen-presenting cells and support superantigen-induced proliferation of resting T cells; however, it remains unknown whether keratinocytes function in situ with T cells via a non-contact mechanism. The current study used a transwell co-culture system and demonstrated, for the first time to the best of the authors' knowledge, that HaCaT cells (the human keratinocyte cell line) did induce T cell proliferation via indirect contact. The data further indicated that exosomes, small membrane vesicles that transfer antigens to recipient cells, are also involved in the superantigen-associated immunity of keratinocytes. The current study provided experimental evidence that HaCaT-exosomes contained MHC I and II, and could interact with T cells. In addition, following interferon. stimulation, Staphylococcal aureus enterotoxin B-loaded HaCaT cells secreted exosomes to induce the proliferation of CD4+ and CD8+ T cells in vitro. This novel biological function of exosomes reveals a new mechanism of how keratinocytes participate in bacterial superantigen-induced immune responses.