One of the booths was showing off a game, called "Killer T-Cell" if I remember correctly, based on some local university research. You'd move a little T-Cell around, through a changing pink maze of good tissue, to absorb & destroy any cancerous (purple?) cells that popped up.
It used hi-res mode but seemed to be played on a grid based on the Apple ][+'s low-res mode – and sometimes that mode flashed through as well. (I can't remember if that was a glitch or purposeful effect.) It was pretty crude in graphics and gameplay, but we bought it, for maybe $5 or $10, on a 5.25" floppy – moreso for the novelty and intellectual content than anything else.
Over 37 years ago, that game conveyed to me the idea that people probably get a lot of microcancers all the time, which are routinely cleaned up by the immune system's T-cells, and only become a problem when the immune system is finally overwhelmed or tricked.
Dr. Allison's Wikipedia page suggests he was at Houston's MD Anderson Cancer Center at that time, in his early 30s. I wonder if the game was motivated by his research... or even if he was the person who sold me that game.