James Allison's T-cell discovery technique
Well so here's the paper, at least on Dr. Allison's side. Mind you, the discovery is shared by a number of individuals for their combined effort.

So what they did is took mice and immunized them with T-cell lymphoma cells. The mice would essentially produce B cells against the lymphoma cells. And so we know that B cells produce antibodies, and hybridoma methods exploit the B cells to get a lot of that antibody. With their constructed hybridoma library, they could look at reactivity of antibodies produced against the lymphoma cells against the reactivity of the same antibody against other cells. They ended up finding 1/43 antibodies, which they dubbed 124-4O, reacted to their lymphoma line, but not to other cells.

With a pull-down assay, they isolated the receptor and determined it was a heterodimeric glycoprotein. A step further, they looked at both B cells and T cells, then, and were able to detect similar structures in the T cells, but not in the B cells.

Someone correct me If I'm wrong, though.