Thapsigargin-Stimulated LAD2 Human Mast Cell Line Is a Potent Cellular Adjuvant for the Maturation of Monocyte-Derived Dendritic Cells for Adoptive Cellular Immunotherapy

Abstract

The preparation of dendritic cells (DCs) for adoptive cellular immunotherapy (ACI) requires the maturation of ex vivo-produced immature(i) DCs. This maturation ensures that the antigen presentation triggers an immune response towards the antigen-expressing cells. Although there is a large number of maturation agents capable of inducing strong DC maturation, there is still only a very limited number of these agents approved for use in the production of DCs for ACI. In seeking novel DC maturation agents, we used differentially activated human mast cell (MC) line LAD2 as a cellular adjuvant to elicit or modulate the maturation of ex vivo-produced monocyte-derived iDCs. We found that co-culture of iDCs with differentially activated LAD2 MCs in serum-containing media significantly modulated polyinosinic:polycytidylic acid (poly I:C)-elicited DC maturation as determined through the surface expression of the maturation markers CD80, CD83, CD86, and human leukocyte antigen(HLA)-DR. Once iDCs were generated in serum-free conditions, they became refractory to the maturation with poly I:C, and the LAD2 MC modulatory potential was minimized. However, the maturation-refractory phenotype of the serum-free generated iDCs was largely overcome by co-culture with thapsigargin-stimulated LAD2 MCs. Our data suggest that differentially stimulated mast cells could be novel and highly potent cellular adjuvants for the maturation of DCs for ACI.

Mast Cells and Dendritic Cells as Cellular Immune Checkpoints in Immunotherapy of Solid Tumors

“…In this regard, the interaction of MCs with DCs may come with an advantage in the ex vivo preparation of DCs. In our previous work, we found that a stimulated human LAD2 MC line could be a highly potent cellular adjuvant for the maturation of ex-vivo-produced human-monocyte-derived DCs for ACT [ 157 ]. This high adjuvant potency was conditioned by previous MC stimulation with thapsigargin, an inhibitor of sarco/endoplasmic reticulum Ca 2+ -ATPases (SERCA) [ 158 , 159 ], which induces a strong mobilization of intracellular calcium followed by fast and extensive degranulation of LAD2 MCs [ 160 ].…”

“…Such previously stimulated and rinsed LAD2 MCs were, unlike their non-stimulated or FcεRI-stimulated counterparts, able to mature monocyte-derived DCs, which were even refractory to the maturation with polyinosinic:polycytidylic acid (poly I:C), a toll-like receptor-3 agonist often used for the production of matured DCs for ACT-based cancer cellular immunotherapy [ 154 , 155 ]. Moreover, the study showed that the adjuvant effect was still notable even when the MC:DC ratio was 1:150 [ 157 ]. This maturation efficiency indicated that a very small number of MCs can promote DC maturation.…”

Mast Cells: When the Best Defense Is an Attack?

“…Considerable attention has been given to the role of MCs in regulating T-cell function, either directly or indirectly, through actions on dendritic cells (DCs). In this issue, Taborska et al [ 2 ] show that differentially stimulated MCs could be novel and highly potent cellular adjuvants for the maturation of DCs, and this ability opens a new avenue to use activated MCs for adoptive cellular immunotherapy. This procedure requires the maturation of ex vivo-produced immature DCs to mount an immune response against the antigen-expressing cells.…”