Staining and serological characteristics of the AC-30 pattern in HEp-2 IIFA: a comparative study with AC-2 pattern

Area of Science:

• Immunology
• Clinical Chemistry
• Autoimmunity

Background:

• Antinuclear antibody (ANA) testing is crucial for diagnosing autoimmune diseases.
• The HEp-2 indirect immunofluorescence assay (IIFA) is a standard method for ANA detection, yielding various patterns.
• The AC-30 pattern's origin and relationship with other ANA patterns, particularly AC-2, require clarification.

Purpose of the Study:

• To investigate the distinct staining and serological characteristics of the AC-30 pattern.
• To differentiate the AC-30 pattern from the AC-2 pattern in ANA testing.
• To explore the role of anti-DFS70 antibodies and homogeneous patterns in AC-30 formation.

Main Methods:

• Recruited 184 patients undergoing routine ANA testing.
• Analyzed 47 patients with AC-30 pattern (Cohort 1) and 137 with AC-2 pattern (Cohort 2).
• Conducted anti-DFS70 antibody detection, DFS70 antigen adsorption assays, and pattern simulation studies.

Main Results:

• Anti-DFS70 antibodies were detected in 97% of Cohort 1 and 100% of Cohort 2.
• Simulated AC-30 patterns by mixing AC-2 with homogeneous patterns, especially at higher titers.
• Observed a higher prevalence of homogeneous nuclear staining post-DFS70 adsorption in Cohort 1 (79%) vs. Cohort 2 (62%).
• Found non-autoimmune conditions more common in Cohort 1 among samples with homogeneous patterns post-adsorption.

Conclusions:

• The AC-30 pattern may arise from lower anti-DFS70 antibody levels or concurrent high-titer homogeneous patterns, differentiating it from AC-2.
• These findings suggest a complex interplay of antibodies contributing to specific ANA IIFA patterns.
• Larger studies are warranted to validate these observations and their clinical implications.