A Phase 1, Multicenter, Single-arm, Dose-escalation Study of CC-97540 (BMS-986353), CD19-Targeted NEX-T Chimeric Antigen Receptor (CAR) T Cells, Evaluating Safety and Tolerability in Participants With Autoimmune Neurological Diseases: Relapsing Forms of Multiple Sclerosis (RMS), Progressive Forms of Multiple Sclerosis (PMS), or Refractory Myasthenia Gravis (MG).

Inclusion Criteria \- Relapsing forms of Multiple Sclerosis (RMS) - Cohort 1. i) Participants must have an Expanded Disability Status Scale (EDSS) of ≥ 3.0 and ≤ 5.5. ii) Participants must have a diagnosis of Multiple Sclerosis (MS) with relapsed/refractory MS or conversion to active secondary progressive multiple sclerosis (aSPMS), and worsening of disease within 12 months prior to Screening and while on treatment with a high-efficacy DMT for at least 6 months. \- Progressive forms of MS - Cohort 2. i) Participants must have an EDSS ≥ 3.0 and ≤ 6.0. ii) Participants must have a diagnosi…