3D visualization of sex differences in the immune response to influenza infection in the mouse lung

Recent developments of imaging techniques, including histo-cytometry and a new tissue clearing and staining protocol called Clearing-enhanced 3D (Ce3D), allow for high-resolution, 3D multiplex quantitative imaging and analysis of cell populations in intact organ material. We have established a panel of 10–14 markers for use in Ce3D-cleared 250μm-thick sections of lung tissue to visualize both innate and adaptive aspects of the immune response as comprehensively as possible. This panel, combined with quantitative analysis provided by histo-cytometry, allows for the collection of larger, more informative imaging datasets than typically generated by conventional histochemistry methods. In our study, we applied these techniques to the mouse model of influenza A virus (IAV) infection to investigate the patterns of immune cell distribution and viral spread in the lungs of male and female mice. In C57BL/6J mice, we observed increased mortality in female mice compared to males when infected with the same dose of the lethal PR8 strain of IAV. Literature research as well as data from the infection of different transgenic mouse lines suggest that higher levels of innate inflammation in female mice may lead to the observed difference in mortality. Ce3D multiplex images show multiple differences in the distribution of both innate immune cells and infected areas in lungs from male and female mice. This study will contribute to a better understanding of both the immune response to IAV infection and sex differences in immunity in general, potentially leading to better design of tailored vaccines and treatments in the future.