Inclusion Criteria:

• Diagnosis of CVID according to the international consensus document (ICON):
  • Age 4 years or above;
  • Serum IgG at least 2 standard deviations below the age adjusted normal;
  • Decreased serum IgA and/or serum IgM;
  • Abnormal specific antibody response to immunization;
  • Exclusion of secondary immunodeficiency.
• On replacement immunoglobulin for at least 6 months and willing to maintain throughout study.
• Granulomatous-lymphocytic interstitial lung disease with a lymphocytic component diagnosed by lung biopsy prior to study entry, wedge biopsy preferred.
• Persistence or worsening of interstitial lung disease measured on serial CT imaging of the lung at least 6 months apart, with the latest assessment within 2 months of study entry.
• Signed written informed consent.
• Willing to allow storage of biological specimens for future use in medical research.
• Females of childbearing potential must use a highly effective form of birth control such as hormone-based contraceptive, intrauterine device, or double barrier method.

Exclusion Criteria:

• History of hypersensitivity to abatacept or any of its components.
• Has received any lymphocyte depleting agents including anti-CD20 monoclonal antibodies, alemtuzumab, ATG in the preceding 6 months.
• Has received abatacept, cyclophosphamide, tumor necrosis factor inhibitors, or pulse steroids (defined as >15mg/kg/day of methylprednisone or corticosteroid equivalent) within the past 3 months.
• History of HIV infection (positive PCR).
• Chronic untreated hepatitis B or C (positive PCR).
• Active tuberculosis (TB) by positive QuantiFERON gold. If history of latent TB, then must supply evidence of completing treatment.
• Persistent Epstein-Barr Virus (EBV) load ≥ 1,000 units/mL blood checked twice at least 1 month apart.
• Other uncontrolled infections.
• Live vaccine given within 6 weeks of the start of the trial.
• Malignancy or treated for malignancy within the past year.
• Currently pregnant or breast feeding.
• Life expectancy less than 1 month.
• Subjects unwilling to self-administer or have a parent/caregiver self-administer subcutaneous injections at home.
• Other conditions that the investigators feel contraindicate participation in the study.

Eligibility last updated 12/22/21. Questions regarding updates should be directed to the study team contact.