Defending and integrating an organism by the immune system.

The Integrity model proposes that the adaptive immune response defends, protects and keeps vigilance over the unity of an organism. These functions conceptually rely on three signals that can explain them. All signals have a dual character. The signal-1 is the recognition of antigen or peptide/MHC ligand. The signal-2 comprises either help and costimulation or suppression and coinhibition. Lastly, the signal-3 signals tissues' condition, state or integrity. A part overlaps with the Danger-associated molecular patterns, and the other part should be detected by putative cell-surface molecules, intracellular factors or epigenetic events. They are called the Integrity-associated molecular patterns (IAMPs). The IAMPs originate from damaged (positive signal-3) or undamaged (negative signal-3) tissues. The positive signal-3 would induce costimulatory signal-2, whereas the negative signal-3 would induce coinhibitory signal-2 in APCs. However, in analogue reality, we might more likely encounter a range of signals supposedly sensed by a group of responder cells and integrated overtime (quorum sensing). The predominant option would sway the decision of the immune system to perform either defence or protection (active tolerance). Thus, the quorum sensing supposedly delivers two qualitative thresholds for T (and B) cells' decisions to defend or suppress. If these were not attained, the vigilance (anergy) of adaptive immunocytes for T-dependent antigens would ensue. These functions provide defence against pathogens and preservation of unity/integrity of an organism, which in turn permits protection of commensals.