IL40: A Newly Described Cytokine With Conflicting Measurements and Detection Variability-Are There Different Forms?

Area of Science:

• Immunology
• Cytokine Biology

Background:

• Interleukin-40 (IL40) is a cytokine encoded by C17orf99 with largely unknown function, though linked to B-cell biology and elevated in rheumatic diseases.
• Current research primarily relies on commercial sandwich ELISAs for IL40 quantification in serum/plasma.

Purpose of the Study:

• To investigate discrepancies between two commercial IL40 ELISAs (Mybiosource and Abbexa).
• To evaluate IL40 levels in patients with ANCA-associated vasculitis and rheumatoid arthritis (RA).
• To compare the binding specificities of different IL40 detection methods.

Main Methods:

• Comparison of IL40 plasma levels using Mybiosource and Abbexa ELISAs.
• Analysis of IL40 levels in patient cohorts including ANCA-associated vasculitis, RA, and RA-L.
• Antibody pre-adsorption experiments to assess target binding.
• Western blot and ELISA using a Human Protein Atlas (HPA) antibody.

Main Results:

• Significant discrepancies were observed between Mybiosource and Abbexa IL40 ELISAs, with Abbexa showing higher plasma levels.
• IL40 (Abbexa) was not elevated in patients with vasculitis or RA compared to healthy donors.
• Abbexa IL40 levels correlated with BAFF and APRIL.
• Neither commercial ELISA detected recombinant IL40, while an HPA antibody did.
• Mybiosource and Abbexa capture antibodies bound the same target but detected different IL40 forms.

Conclusions:

• Commercial IL40 ELISAs exhibit significant discrepancies, potentially due to different detection of IL40 forms.
• IL40 levels were not elevated in the studied rheumatic disease cohorts using the Abbexa assay.
• The findings highlight challenges in interpreting commercial antibody-based assay results and suggest potential structural variations of IL40.