Cell Density Plays a Critical Role in Ex Vivo Expansion of T Cells for Adoptive Immunotherapy

Abstract EN

The successful ex vivo expansion of a large numbers of T cells is a prerequisite for adoptive immunotherapy.

In this study, we found that cell density had important effects on the process of expansion of T cells in vitro.

Resting T cells were activated to expand at high cell density but failed to be activated at low cell density.

Activated T cells (ATCs) expanded rapidly at high cell density but underwent apoptosis at low cell density.

Our studies indicated that low-cell-density related ATC death is mediated by oxidative stress.

Antioxidants N-acetylcysteine, catalase, and albumin suppressed elevated reactive oxygen species (ROS) levels in low-density cultures and protected ATCs from apoptosis.

The viability of ATCs at low density was preserved by conditioned medium from high-density cultures of ATCs in which the autocrine survival factor was identified as catalase.

We also found that costimulatory signal CD28 increases T cell activation at lower cell density, paralleled by an increase in catalase secretion.

Our findings highlight the importance of cell density in T cell activation, proliferation, survival and apoptosis and support the importance of maintaining T cells at high density for their successful expansion in vitro.