Characterization of natural killer and natural killer-like T cells derived from ex vivo expanded and activated cord blood mononuclear cells: implications for adoptive cellular immunotherapy.

OBJECTIVE: Cord blood (CB) is limited by the absence of available donor effector cells for post-unrelated CB transplantation adoptive cellular immunotherapy. We reported the ability to ex vivo expand (EvE) CB mononuclear cells (MNC) after short-term incubation with anti-CD3, interleukin (IL)-2, IL-7, and IL-12 (antibody/cytokine [AB/CY]) into subpopulations of CD3(-)/56(+) natural killer (NK) cells with enhanced in vitro and in vivo tumor cytotoxicity.

MATERIALS AND METHODS: We compared 2- vs 7-day EvE of rethawed CB MNCs in AB/CY and activation of NK and NK-like T (NKT) cell (CD3(+)/56(+)) subsets expressing specific NK-cell receptors along with IL-15, IL-18, and interferon-gamma production.

RESULTS: Nonadherent total cell number were significantly increased at day 7 (p<0.001) along with NK-cell number (20-fold) and an enrichment in NKT-like subsets (36-fold). There was no change in the NK(dim) subset; yet the NKT(bright) and NKT KIR3DL1(dim) subsets were significantly increased (p<0.05). NK cells expressing the inhibitory natural cytoxicity receptor CD94/NKG2A were decreased (p<0.001), while those expressing activating natural cytoxicity receptor CD94/NKG2D receptor and activating NK and NKT KIR2DS4 subsets were significantly increased (p<0.001). IL-18 and interferon-gamma protein production was also significantly increased (p<0.001 and p<0.05, respectively). Lysosomal-associated membrane protein-1 and granzyme B expression were increased (p<0.001 and p>0.01, respectively), which correlated with the significant increase in NK, LAK, and tumor cytotoxicity of the EvE cells.

CONCLUSION: This study demonstrates that previously cryopreserved and rethawed CB MNCs can be EvE up to 7 days to yield viable and activated NK and NKT-like subsets that appear to be cytolytic based on the cell repertoire and could be utilized in the future as adoptive cellular immunotherapy post-unrelated CB transplantation.