CD19 and rheumatoid arthritis: •Serum anti-MAA (IgA/IgM) Ab higher RA-ILD vs. RA alone•RA-ILD odds ratio of 2.5 (individual with 3 positive isotypes vs. 0-1 positive isotype)•MAA antigen co-localized with citrulline, CD19+ cells, type II collagen, and vimentin in RA-ILD