Immunological memory diversity in the human upper airway.

Abstract

The upper airway is an important site of infection, butimmune memory in the human upper airway is poorly understood, with implications for COVID-19 and many other human diseases1-4. Here we demonstrate that nasal and nasopharyngeal swabs can be used to obtain insights into these challenging problems, and define distinct immune cell populations, including antigen-specific memory Bcells and T cells, in two adjacent anatomical sites in the upper airway. Upper airway immune cell populations seemed stable over time in healthy adults undergoing monthly swabs for more than 1 year, and prominent tissue resident memory T (TRM)cell and B (BRM) cellpopulations were defined. Unexpectedly, germinal centre cells were identified consistently in many nasopharyngeal swabs. In subjects with SARS-CoV-2 breakthrough infections, local virus-specific BRMcells, plasma cells and germinal centre B cells were identified, with evidence of local priming and an enrichment of IgA+ memory B cells in upper airway compartments compared with blood. Local plasma cell populations were identified with transcriptional profiles of longevity. Local virus-specific memory CD4+ TRM cellsand CD8+ TRM cellswere identified, with diverse additional virus-specific T cells. Age-dependent upper airway immunological shifts were observed. These findings provide new understanding of immune memory at a principal mucosal barrier tissue in humans.