NASAL KLEBSIELLA PNEUMONIAE IMMUNIZATION GENERATES HETEROGENEOUS POPULATIONS OF RESIDENT MEMORY B CELLS AND PLASMA CELLS IN THE LUNG

Mar del Plata

Congreso; LXX REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INMUNOLOGÍA (SAI) & 3ER CONGRESO FRANCO-ARGENTINO DE INMUNOLOGÍA (FAIC); 2022

Sociedad Argentina de Inmunología

The development of a proper adaptive immune response against different microbes protects against future challenges through thegeneration of memory B and T cells. Memory immune responsescan be induced locally or systemically after immunization or infection.Systemic immunizations generate circulatory memory B andT cells but local immunizations induce both circulatory and tissueresident memory T and B cells (TRM and BRM). The development ofmemory cells in the lung is crucial to quickly deal with respiratorytract infections. Our previous results indicate that intranasal immunizationwith heat-killed Klebsiella pneumoniae (Kp) protects micefrom infection through the generation and re-activation of CD4 TRM cells. Based on these results, our goal was to characterize memoryBRM after intranasal immunization. C57Bl/6 mice were intranasallyimmunized on day 0 and 7 with heat killed Kp. On day 30 post immunization,mice were intravenously (iv) injected with anti-CD45-A700antibody as a tool to exclude circulating immune cells in future analysis;5 minutes after that mice were sacrificed, and lung collected.Then, we sorted lung CD45iv negative and CD4negative cells from naïveand immunized mice to perform single cell RNA-seq and SingleRto identify clusters of hematopoietic and non-hematopoietic cells.Among hematopoietic cells, we selected the B cell cluster using asingle-cell-Gate tool to evaluate BRM heterogeneity. As expected, thenumber of lung infiltrating B cells was higher in immunized versusnaïve mice. Immunized mice had heterogeneous populations of BRMbased on cluster numbers (6 clusters immunized mice vs 3 clustersnaïve mouse) and also an increase in IgA+ resident plasma cellscompared with naïve mice. Preliminary evaluation using flow cytometryshows agreement with single cell RNA-seq data. In conclusion,we determined that intranasal Kp immunization generates differenttypes of BRM whose specificity and function will be further evaluated.