The purpose of this study is to assess if a 12-week exercise program is safe, practical, and acceptable for adults with primary antibody deficiencies. It also looks at whether the program can improve the quality of life and help the immune system work better.

Study activities will include:

Completion of health questionnaires Participation in a 12-week exercise program using a mobile application Having your exercise activity tracked through the mobile application Reporting any symptoms or infections that develop Providing blood samples for immune-related testing at your patient visits. Completion of assessments at the beginning and end of study

Inclusion Criteria:

• Diagnosed with one of the following primary antibody deficiencies: IgG subclass deficiency, selective IgA deficiency, selective IgM deficiency, or specific antibody deficiency
• Receiving care in the Section of Rheumatology, Allergy & Immunology
• Able and willing to participate in a moderate-intensity exercise program. Patients will be screened using the American College of Sports Medicine (ACSM) Pre- participation Screening Guidelines. This algorithm assesses patients for cardiovascular, renal, and metabolic disease. Those patients determined to not require further medical clearance to participate in exercise will be included.

Exclusion Criteria:

• Receipt of immunoglobulin (Ig) replacement therapy
• Use of immunosuppressive or immunomodulatory medications (e.g., chronic systemic corticosteroids, B-cell-depleting therapies)
• Medical contraindications to moderate-intensity exercise as determined by clinical assessment using the previously discussed ACSM Pre-participation Screening Guidelines.
• Other risk factors/medical conditions that would limit safe participation in exercise as determined by clinical assessment, including active rheumatologic conditions including active rheumatoid arthritis.