Figure 2.

Local immune response to infectious P. aeruginosa biofilm. The innate immune response recognizes pathogen associated molecular patterns (PAMPs) expressed on P. aeruginosa, and biofilm-associated molecular patterns (BAMPs) present in the biofilm matrix. Detection of BAMPs and PAMPs by PMNs and macrophages is mediated by pattern recognition receptors (PRRs). Binding of BAMPs and PAMPs to PRRs stimulates the PMNs and macrophages resulting in consumption of O₂ for liberation of tissue-toxic reactive oxygen species (ROS) and nitric oxide (NO). Additional responses by the PMNs include secretion of proteases that may cause proteolytic tissue lesions while the macrophage may further enhance the inflammation by emitting pro-inflammatory cytokines such as TNF-α, Il-1, IL-6, IL-8, and IL-12. The effector cells of the adaptive immune response mainly reside distantly such as the T-cells and the B-cells in the secondary lymphoid organs and the plasma cells in the bone marrow. Activated T-cells may release cytokines that further reinforces the inflammation by stimulating the accumulation and activation of PMNs and production of IgG. The contribution of the increased accumulation of activated PMNs to the local inflammation is further accelerated by binding of antigens to IgG, leading to immune complex mediated stimulation of the PMNs and activation of the classical complement pathway.