Systemic immunization of autoimmune-prone SWXJ mice with Coch 131–150, an RXXS peptide from the abundant IE extracellular protein cochlin, induced CD45⁺ cell cochlear infiltration and ASNHL in mice within 5–6 weeks. Lymph node (LN) or spleen cells placed in culture 8–10 days after immunization proliferated, as evidenced by ³H-thymidine incorporation, and showed a Th1 cytokine profile (high levels of IFN-γ and low levels of IL-4 production) after restimulation in vitro with Coch 131–150. Flow cytometry confirmed preferential reactivation of CD4⁺ T cells. After restimulation in vitro with peptide, the total population or the CD4⁺-enriched population (>95%) of cells induced ASNHL 6 weeks after passive transfer to naive, irradiated, histocompatible recipient mice. The same results were obtained after priming, restimulation, and transfer of CD4⁺ T cells specific for a KXXS peptide from a second IE protein, β-tectorin 71–90, but not with ovalbumin as Ag (16).