What does an elliptical galaxy contain?
Typically, a bunch of old, low-mass stars, and dust. Not much gas.
Typical elliptical galaxies are thought to be born a long time ago (~1Gyr or less, after the BB) either from monolithic collapse of primordial gas or by merging processes, but in any case, they have been around for a long time, and have not much hydrogen gas left to be turned into stars. Thus, they contain mostly old, low-mass stars because the young massive ones would just die within a few 10s to 100s million years, while low-mass stars last for billions of years. Dust contents varies from galaxy to galaxy.
However, it should be noted that there are some cases where elliptical galaxies presents residual star formation, or possess star forming outer regions, so rejuvenation is still probable if gas replenishment occurs (somehow; for e.g., a merging event with a gas-rich spiral).