In T lymphocytes, the sole pathway for Ca++ entry following antigen-receptor binding is through store-operated Ca++-release-activated Ca++ (CRAC) channels.  These channels are made up of the pore-forming subunit ORAI1 and the stromal interaction molecule 1 (STIM1), a protein that functions as a Ca++ sensor and activates the CRAC channels, migrating to the plasma membrane from endoplasmic reticulum (ER)-like sites which act as the Ca++ store.  A related molecule, STIM2, acts to inhibit the STIM1-mediated store-operated Ca++ entry, and can form complexes with STIM1, suggesting they may play a coordinated role in controlling Ca++ entry.  At least three isoforms of STIM2 are known to exist.  This STIM2 antibody is predicted to have no cross-reactivity to STIM1.