DSince the start of the Covid-19 pandemic, the multiple facets of the immune response have received unprecedented attention. Who might have predicted, two years ago, that we would be so exposed to the notion of herd immunity, that we would all have heard of cytokine storms, that interferons, cytotoxic T lymphocytes or monoclonal antibodies s would frequently feature in the daily press? Over this period, one of the most salient aspects of the immune response is perhaps its temporality. We were constantly reminded that immunity once morest a pathogen takes several days to build up following initial exposure to the virus or vaccination: this is “acquired” immunity. The emergence of variants which, like Omicron, escape the antibodies developed once morest previous viral strains has, moreover, illustrated how closely this acquired immunity was specific to a given pathogen.
This specific, but delayed, immunity is usually opposed to the body’s first lines of defense during an infection, collectively referred to as innate immunity. As soon as an intrusion is spotted, the cells in contact with the microbe begin to produce and release molecular warning signals. These signals cause the dilation of blood vessels, leading to the appearance of redness and a feeling of warmth: this is inflammation. The dissemination of warning signals and the increase in the blood supply make it possible to attract different families of white blood cells to the spot; the most numerous are neutrophils, cells capable of killing microorganisms by bombarding them with toxic compounds, or by engulfing them.
Court-circuit
In this process, the microbe that has entered the organism is not precisely identified; its presence is identified by molecular signatures which testify to an anomaly, without providing information on its virulence. For example, if the cells that make up our tissues come into contact with certain components of the bacterial surface, they trigger an inflammatory response because these molecules have no place inside the body. Most of these intrusion indicators are fairly common molecules in their nature, and are therefore not the prerogative of pathogenic microbes. The inflammatory response then allows the body to react quickly to block the road without discrimination, with some collateral damage.
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