TLR9 and respiratory system disorder: However, post-second doses showed an increase in certain parameters (the proportion of lymphocytes expressing TLR9 and monocytes expressing TLR3 and TLR9), indicating a significant protective effect against respiratory diseases, because stimulation of TLR 9 located on B-lymphocytes and TLR3 on lymphocytes (T, B and NK cells), dendritic cells and monocytes, as well as fibroblasts, is most likely responsible for the proper defense of organisms against pathogens (mainly viruses) due to their intracellular location and thanks to the normal production of IFN-α/β as a result.