Mast cells (MCs) are immune cells residing in tissues where pathogens are first encountered. It has been indicated that MCs might also be involved in setting the outcome of T-cell responses. However, little is known about the capacity of human MCs to express MHC class II and/or to capture and present antigens to CD4(+) T cells. To study the T-cell stimulatory potential of human MCs, CD34(+) stem cell derived MCs were generated. These cells expressed HLA-DR when stimulated with IFN-γ, and, importantly, presented peptide and protein for activation of antigen-specific CD4(+) T cells. The interplay between MC and T cell led to increased HLA-DR expression on MCs. MCs were present in close proximity to T cells in tonsil and expressed HLA-DR and CD80, indicating their ability to present antigens to CD4(+) T cells in T-cell areas of human LNs. Our data show that MCs can present native antigens to human CD4(+) T cells and that HLA-DR expressing MCs are present in tonsil tissue, indicating that human MCs can directly activate T cells and provide a rationale to study the potential of MCs to prime and/or skew human T-cell responses.
Keywords: Antigen presentation; CD4+ T lymphocytes; Mast cell.
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