When a T-cell meets its matching antigen, the first thing it needs is a sharp rise in cytosolic calcium. That calcium wave flips dozens of molecular switches, kick-starting gene expression and the rapid division that turns a lone sentry into a small army of defenders. Yet exactly which proteins make sure the wave breaks at the right moment has remained murky.

Starting in yeast, I noted that heat-stressed cells ramp up production of Hsp90, a highly conserved “helper” protein that keeps other molecules folded and ready. Yeast strains with plenty of Hsp90 divided more smoothly and survived harsh conditions better than strains in which the protein was scarce. Calcium measurements told the same story: without Hsp90, signaling spikes were blunted.

Armed with these clues, I got the opportunity to join the Calcium-Signalling Group (SFB 1328, University Medical Center Hamburg-Eppendorf) under the guidance of Professor Andreas Guse and Dr. Feng Gu. In human Jurkat T-cells I blocked Hsp90 with a specific inhibitor and used the fluorescent dye Fura-2 to watch calcium levels in real time. The result was decisive: cells with inhibited Hsp90 produced a much weaker calcium signal than untreated controls, and they entered proliferation far more slowly.

Because sustained calcium signaling is crucial for both T-cell activation and the cascade that wakes other immune cells, my work could position Hsp90 as a potential dial for tuning immune responses—damp it down for autoimmune disease or boost it to sharpen cancer immunotherapy.