Controlling Hyperactive Immunity With Long-lived Lymphocytes

Inclusion Criteria: * Participants must be at least 18 years of age at the time of signing the informed consent. * Up to date vaccination status and no planned vaccinations for post 3 months infusion * Adequate haematological, liver and renal function * Willing to undergo annual influenza vaccination * Willing to enter a 15-year follow-up * Eastern Cooperative Oncology Group (ECOG) performance status grade \< 3 * Able and willing to use a highly effective method of contraception * Stable dose of steroid prior to screening Specific inclusion criteria for participants with difficult to treat rheumatoid Arthritis (D2TRA) only: * Diagnosis of Rheumatoid Arthritis (RA) per 2010 ACR-EULAR criteria * Diagnosis of D2TRA per 2021 EULAR criteria * Evidence of clinically active disease a defined by validated clinical or laboratory results consistent with standard definitions of active RA * Evidence of inflammation in target joints used for the DAS28 CRP assessment Specific inclusion criteria for participants with diffuse cutaneous systemic sclerosis (dcSSc) only: * Diagnosis of dcSSc as per the 2013 ACR-EULAR criteria * Serologically positive for antinuclear antibodies * Failure to respond sufficiently to immunomodulatory disease modifying anti-rheumatic drugs (DMARDs). * Skin involvement with a total modified Rodnan Skin Score of at least 15 * Evidence of lung fibrosis based on imaging or pulmonary function testing * Evidence of active disease based on a validated SSc activity assessment Exclusion Criteria: * Presence of a significant medical condition(s), or clinically significant laboratory abnormality * History or concern of autoimmune diseases other than those under study * Active infection, or recurrent chronic infection requiring intervention * Immunodeficiency or receiving immunoglobulin replacement therapy * Past or current infection with hepatitis B or C, tuberculosis, syphilis, or HIV * Clinically significant cardiac dysfunction or severe pulmonary impairment * Use of investigational agents within a pre-defined period prior to study screening * Received a previous cell therapy * Received certain B cell related experimental therapies in a clinical trial with the past year * Any solid organ, bone marrow or stem cell transplant * History of malignancy in the past 5 years * Receiving prohibited medication that cannot be stopped at screening