A Study to Assess Adverse Events, How the Drug Moves Through the Body and Effectiveness of Intravenous Infusions of ABBV-319 in Adult Participants With Systemic Lupus Erythematosus (SLE), Sjogren's Disease (SjD) and Rheumatoid Arthritis (RA)

Inclusion Criteria:

• Systemic Lupus Erythematosus (SLE) Population - Clinical diagnosis of SLE at least 6months prior to Screening as defined by the 2019 European Alliance of Associationsfor Rheumatology (EULAR)/American College Of Rheumatology (ACR) classificationcriteria for SLE and a positive antinuclear antibody (ANA) >= 1:80 drawn atScreening.

• SLE Population - Anti-double stranded DNA (dsDNA), anti-Smith (Sm),anti-ribonucleoprotein (RNP), or anti-Sjogren's syndrome Ag A (SSA) Abs above theupper limit of normal (ULN).

• Sjogren's Disease (SjD) Population - Primary diagnosis of SjD at least 6 monthsprior to Screening as defined by the ACR/EULAR 2016 Criteria.

• SjD Population - EULAR Sjogren's Syndrome Disease Activity Index (ESSDAI) >= 5 atScreening.

• SjD Population - EULAR Sjogren's Syndrome Patient Reported Index (ESSPRI) >= 5 atScreening.

• Rheumatoid Arthritis (RA) Population - Clinical diagnosis of RA and fulfilling the 2010 ACR/EULAR classification criteria for RA.

• RA Population - Rheumatoid Factor (RF) or ACPA above the ULN at Screening.

• RA Population - Confirmation of at least moderate disease activity at Screening,defined by both of the following disease activity criteria:

• Presence of at least 6 swollen and 6 tender joints at Screening using the 68 (tender)/66 (swollen) joint count.

• hs-CRP ≥3 mg/L.

Exclusion Criteria:

• History of infection as defined in the protocol.

• Any of the medical diseases or disorders listed in the protocol.

• History of clinically significant (per investigator's judgment) drug or alcoholabuse within the 6 months prior to Screening.

• Any planned elective surgery that would impact study procedures or assessmentsthrough the completion of the Day 365 assessments.

• Any clinically significant ECG abnormalities at Screening.

• RA-Specific Exclusion Criteria - History of RA overlap syndromes, including but notlimited to, SLE, SjD, scleroderma, mixed connective tissue disease, or polymyositis.