Enhanced NK Cell Activation, Cytotoxicity and Ex-Vivo Expansion (EvE) of Cryopreserved Cord Blood (CB) Natural Killer (NK) Cells: Potential Role for CB NK Cells in Adoptive Cellular Immunotherapy (ACI).

CD56⁺ NK subsets exhibit differential NK receptors (NKR ) such as NCR profiles including killer-Ig-like receptors (KIR), C-lectin (NKG2) and natural cytoxicity receptors (NCR) involved with tumor target recognition (Farag et al Blood, 2002). NK cell activation and NK mediated cytolysis is induced by several NKRs such as NCR (i.e. NKp44, NKp46) and NKG2 surface receptors like NKG2D (Moretta et al, Curr Opinion in Immunol, 2004). Target cell killing by activated NK cells via the granule-dependent pathway is a common mechanism of NK and CTLs and degranulation is followed by the expression of lysosomal-associated membrane protein-1 [LAMP-1] on the cell surface (Penack et al, Leukemia, 2005). CB is limited by the absence of available donor effector cells (NK, CTL, LAK and NKT cells) for infusion after UCBT (Cairo, et al, Transfusion, 2005). We have demonstrated the ability to EvE CB in short-term culture (48 hrs) with IL-2, IL-7, IL-12 and anti-CD3 (ABCY) cryopreserved, thawed, recryopreserved, rethawed and EvE (CTCTE) CB with significant increase in CD3⁻/16⁺/56^{+ bright/dim} subsets expressing KIR3DL1, KIR2DL1/S1, KIR2DL2 and CD94/NKG2a (Ayello/Cairo et al BBMT, 2006). In this study, we compared short-term culture (48 hrs) with prolonged cultures (4 to 10 days) on expansion, expression of NCR, NKG2, KIR and cytolytic ability and mechanisms in CTCTE CB. Rethawed nonadherent CB cells were cultured (2–10 days) in serum-free media alone or with anti-CD3 (50 ng/ml), IL-2 (5 ng/ml), IL-7 (10 ng/ml) and IL-12 (10 ng/ml) [ABCY]. NKR expression (CD94, NKG2D, Nkp44 and KIR2DS4), intracellular perforin, granzyme B activity and LAMP-1 receptor (CD107a) expression were determined by flow cytometry. Cytoxicity was measured by europium release assay and tumor targets used were K562, Daudi, neuroblastoma (SHSY5Y) and AML (Kasumi-1) at a 20:1 E:T ratio. C-lectin activating receptor CD94/NKG2D was increased at day 7 vs 2 following ABCY EvE (41.4±0.43 vs 23.7±2.%, p<0.001). Significant increases were seen in activating KIR2DS4 at day 10 vs 2 in ABCY in both CD3⁻/16⁺/56^{+dim and bright} subsets (16.9±0.4 vs 2.1±0.2% and 22.3±0.3 vs 0.9± 0.2%, p<0.001, respectively). In contrast, NCR expression in CD3⁻/16⁺/56^+dim NKp44 subset was significantly decreased at day 10 vs 2 of EvE CB in ABCY (15.2±0.7 vs 27.2±0.7%, p<0.001). Granzyme B expression was increased from day 2 to 10 (25.8± vs 45.1± 1.7%, p<0.001) yet perforin was decreased in EvE CB in ABCY at day 7 vs 2 (68.3±2.19 vs 84.3±1.3%, p<0.001). CD107a expression was significantly increased at day 7 vs 2 in ABCY EvE CB (12.95±1.47 vs 69.34±2.22%, p<0.001). In addition, significant increases in cytolytic activity was demonstrated at day 7 vs 2 of EvE CB cells in ABCY against tumor targets K562 (71.5±±0.81 vs 53.8±3.9%, p<0.001), Daudi (63.9±0.73 vs 31.8±1.8%, p<0.001), SYSY5Y (76.8±6.5 vs 57.5±3.4%, p<0.05) and Kasumi-1 (56.6.5±0.4 vs 38±1.1%, p<0.001). In summary, CB MNC may be thawed at time of CB transplantation, recryopreserved, rethawed at a later date, EvE and activated for up to 10 days to yield significantly increased cytotolytic activity against NHL, AML and neuroblastoma with increased expression of NK KAR KIR2DS4 and granzyme B, LAMP-1 degranulation (NK activation) but decreased NK C-lection CD94/NKG2D, NCR NKp44 and perforin expression.