Monoclonal antibodies RB139 and RB142 recognize citrullinated LL37 by immunofluorescence in histological sections in Systemic lupus erythematosus (SLE) and Rheumatoid arthritis (RA)

Roberto Lande,Cristiano Alessandri,Barbara Tolusso,Carlo Chizzolini,Francesca Spadaro,Immacolata Pietraforte,Kostantino Giannakakis,Fabrizio Conti,Elisa Gremese,Loredana Frasca,Raffaella Palazzo,Mario Falchi,Stefano Alivernini,Francesca Romana Spinelli

doi:10.24450/journals/abrep.2020.e236

Abstract

LL37 is a natural antibiotic, but is also a molecule with pleiotropic functions as well as an immune-modulator. LL37 is produced by epithelial cells and is present in neutrophils’ granules. LL37 alone, or in complex with DNA, can activate inflammatory pathways in psoriasis, systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). In this work, we describe the capacity of two recombinant monoclonal antibodies, RB139 and RB142, previously shown to specifically recognize LL37 in its citrullinated form (cit-LL37) by ELISA, to detect LL37 by immunofluorescence in human inflamed tissues derived from SLE and RA patients. Such antibodies represent previously unavailable tools to detect the presence, the citrullinated state and the exact localization of cit-LL37 in human tissues in health and disease.

Highlights

Human cathelicidin antimicrobial peptide (Uniprot P49913), called CAP18 or FALL39, is encoded by the human gene CAMP
A consistent neutrophil infiltrate was present in the SLEaffected kidney (Fig. 1a)
Since strict colocalization was not often found with MPO, the staining seems to indicate that the antibody RB139 recognized citLL37 expressed in neutrophils that have released their content, as it is possible that LL37 undergoes citrullination outside the cells (Frangou et al, 2019)

Summary

Introduction

Human cathelicidin antimicrobial peptide (Uniprot P49913), called CAP18 or FALL39, is encoded by the human gene CAMP. Geneva University Library Open Access Publications https://oap.unige.ch/journals/abrep | ISSN 2624-8557 are characterized by a neutrophilic inflammation (Cecchi et al, 2014; Frangou et al, 2019). To address whether cit-LL37 is present in the sites of neutrophil infiltrates, we stained the biopsies for myeloperoxidase (MPO), a reliable marker of neutrophils (Cecchi et al, 2014; Frangou et al, 2019).

Results

Conclusion