Adoptive transfer of naive OT-I MitoSnap cells followed by Listeria monocytogenes expressing OVA (LM-OVA) (Fig. 4b) infection demonstrated that heterogeneous inheritance of preM/old mitochondria also occurs in vivo: MitoSnaplo cells being more frequent amongst memory precursors (CD127+) (Fig. 4c) and MitoSnaphi cells exhibiting higher granzyme B expression (Fig. 4d). The gene discussed is GZMB; the disease is infection.