Cellular therapeutics is an emerging field with significant advances in the engineering of immune effector cells, which play a revolutionary role in treatment for cancer. Although most immunomodulatory strategies focus on enhancing T cells – which have proved their ability in successful cellular therapies against leukemia – this strategy may soon face competition. Through several preclinical studies, researchers have discovered new guardian immune cells called chimeric antigen receptor (CAR)-modified natural killer (NK) cells, which show cytotoxic activity against various solid tumor types. The preclinical evidence suggests that NK cells have the same cancer-homing receptors as T cells and but need to be genetically modified to recognize and kill targets.

Naturally, zebrafish are found in places with a large amount of plants. However in laboratories, they are kept in very simple and empty environments, which has negative effects on their welfare. A common issue linked to this is the level of aggression within the group; lack of hiding spaces means victimised zebrafish cannot escape the aggressive individuals. Despite this, researchers worry that adding hiding spaces could reduce the water quality, affect the fish, and influence the experimental results. The aim of this experiment was to see if zebrafish were less aggressive when they had places to hide, compared to when the tank was empty. We also tested which type of hiding space the fish liked the most; this was done by seeing where the fish spent the most time when given the choice.