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-γ 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-γ 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.