Collectively, our results suggest that systemic and gut IgA responses against bacteria originate from discrete anatomical sites with inductive sites in the upper aerodigestive tract likely playing a prominent role in generation of systemic IgA.

Notably, while IgA plasma cells in the bone marrow were almost exclusively of the IgA1 subclass, gut plasma cells showed an equal distribution between IgA1 and IgA2.

Further, by conducting scRNA-seq on isolated plasma cells from paired samples of bone marrow and gut, we map differences in gene expression and VDJ repertoire between the two compartments. We also identify shared clonotypes with reactivity to bacterial antigens.

By isolating bacteria from duodenal biopsies, we show that serum IgA recognizes certain species of the upper GI tract. IgA secreted from gut plasma cells on the other hand showed broader reactivity to different bacteria.

This is great! I would love to join the party.