Enhanced Cytotoxic Function of Natural Killer and CD3+CD56+ Cells in Cord Blood after Culture

Abstract

Rate of immune reconstitution (IR) directly correlates with the number of hematopoietic stem cells (HSC) infused and is particularly delayed in patients undergoing cord blood (CB) transplantation (CBT). Methods to increase the number of CB natural killer (NK) cells have the potential to improve IR after CBT. NK cells are the first lymphocyte population to recover after HSC transplant and are central to preventing early relapse and infection. CB NK cells are low in number and are known to be incomplete in maturation and require activation for effective function. Here, we report a clinically relevant ex vivo expansion method that increases the number of activated CB NK cells. We report a multi-log increase in NK cell number when CB mononuclear cells (CBMC) are co-cultured with interleukin (IL)-2 and IL-15 resulted. Furthermore, NK cells expressing activating receptors and adhesion molecules responsible for cytotoxicity increased throughout culture while inhibitory receptor expression remained low. Additionally, cytotoxic function against various malignancies was significantly enhanced in cultured NK cells but not CD3+CD56+ cells. These data suggest that ex vivo expansion and activation of CB NK cells is a clinically feasible and relevant approach to prevent early infection and relapse after CBT.

Umbilical cord blood–derived cellular products for cancer immunotherapy

“…In addition, expanded CB-NK cells demonstrate anti-tumor activity, both in vitro and in vivo [7,8,15]. Further study of these cells has demonstrated that despite log-fold expansion, CB-NK cells are not exhausted and probably function through NKG2D [16].…”

“…These techniques generally involve a 2-to 4-week cell culture in the presence of interleukin (IL)-2. Additional factors to stimulate NK cell growth include IL-15 [7], artificial antigenpresenting feeder cells [8] and FLT3 ligand [9,10]. Whereas many of these expansions arise from CB mononuclear cells (CMNCs), NK cells can also be differentiated and expanded from CD34 þ cells selected from the CB unit [11e14].…”

NK cell therapy after hematopoietic stem cell transplantation: can we improve anti-tumor effect?

“…Autologous as well as allogeneic NK cells can be purified from peripheral blood apheresis products or obtained from umbilical cord blood (UCB) [18,19]. Additionally, NK cells can be developed from CD34 + UCB stem cells or from induced pluripotent stem cells [20,21].…”

“…Ex vivo expansion methods included single cytokines or cytokine cocktails containing IL-2, IL-15, IL-12 or IL-18 [18,26]. To potentiate proliferation, anti-CD3 antibodies were added to cultures [27].…”

“…With this method, NK cell proliferation can continue for 8-10 weeks before NK cells go into senescence, with NK cells displaying longer telomeres and the capacity of continuous proliferating capacity. For UCB-derived NK cells, proliferation protocols are similar to those used for peripheral blood NK cell expansion and also consist of cytokine combinations in the presence or absence of different feeder cells expressing NK cell-activating ligands (membrane-bound cytokines, 4-1BB) and anti-CD3 antibodies [18,33].…”