Retinoic acid induction of CD1d expression primes chronic lymphocytic leukemia B cells for killing by CD8+ invariant natural killer T cells

- CD1d expression is reduced on B cells from CLL patients.
- CLL B cells have reduced capacity to present glycolipid antigens to iNKT cells.
- Retinoic acid induces CD1d expression by CLL B cells.
- Retinoic acid primes CLL B cells for killing by CD8α+ iNKT cells
- Including retinoic acid in iNKT cell-based therapies may benefit patients with CLL.

Invariant natural killer T (iNKT) cells are cytotoxic T cells that respond to glycolipid antigens presented by CD1d. Therapeutic activation of iNKT cells with α-galactosylceramide (α-GalCer) can prevent and reverse tumor growth in mice and clinical trials involving α-GalCer-stimulated iNKT cells are ongoing in humans. B cells express CD1d, however, we show that CD1d expression is reduced on B cells from patients with chronic lymphocytic leukemia (CLL). B cells from CLL patients pulsed with α-GalCer failed to stimulate cytolytic degranulation by iNKT cell lines, but could present the more potent glycolipid analogue, 7DW8-5. Retinoic acid receptor-α (RAR-α) agonists induced CD1d expression by CLL B cells, restoring their ability to present α-GalCer to CD8α+ iNKT cells, resulting in cytolytic degranulation. Thus, RAR-α agonists can augment the anti-tumor activities of iNKT cells against CLL cells in vitro. Their inclusion in iNKT cell-based therapies may benefit patients with CLL.