Danger signals
"In a 1994 article entitled "Tolerance, Danger and the Extended Family", Matzinger went several steps further by laying out the idea that antigen-presenting cells respond to "danger signals" - most notably from cells undergoing injury, or stress or "bad cell death" (as opposed to apoptosis, controlled cell death). The alarm signals released by these cells let the immune system know that there is a problem requiring an immune response. She argued that T-cells and the immune response they orchestrate occurs not because of a neonatal definition of "self", as in the previous model, nor because of ancient definitions of pathogens, as in Janeway's argument, but due to a dynamic and constantly-updated response to danger as defined by cellular damage."
The Danger Model
The self-non-self model, the predominant model in immunology since the 1950s, began to encounter problems in the late 1980s when immunologists began to recognize that T-cells depend on other cells to pick up and then present the things to which they will respond — and that the T-cell response depends on whether the other cell (known as antigen-presenting cells) is sending activation signals to the T-cells.
In 1989, drawing on the ideas of Thomas Kuhn, Charles Janeway proposed that the old immunological paradigm had reached the limits of its usefulness--or, as he described it, the asymptote of the increase in knowledge which it had brought. Janeway argued that the innate immune system was the real gatekeeper of whether the immune system responded or did not respond. He also argued that the innate immune system used ancient pattern-recognition receptors to make these decisions - recognizing a pathogen by its unchanging characteristics.
Source:Wikipedia
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Jimmy B
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