Final answer:
In the case of a child with strep throat, 'Healing by first intention' is least likely to be activated, as this refers to wound healing without significant scarring, which is not directly related to an infection of the pharynx caused by Streptococcus pyogenes.
Step-by-step explanation:
In the context of a strep throat infection, the child's immune system will indeed activate various defense mechanisms. However, the option that will most likely NOT be activated is 2) Healing by first intention. Healing by first intention refers to the process of wound closure in which the edges of a clean and uninfected wound are brought together and reconnected without the formation of granulation tissue or significant scarring. Strep throat is an infection and inflammation of the pharynx caused by Streptococcus pyogenes, which triggers the immune response but does not involve immediate wound healing as in a cut or surgical incision.
The complement cascade (option 1), including the proteins C3 to C9, would be activated as part of the immune system's response to the infection. Additionally, histamine release (option 3) and the production of antibodies (option 4) would also occur as a response to the foreign pathogen. The arachidonic acid metabolism (option 5) would likely be involved as part of the inflammatory response. Therefore, these responses would all be part of the immune system's reaction to strep throat, unlike healing by first intention.
The classical complement activation pathway is triggered by the binding of an acute-phase protein to a pathogen (option A). This pathway is one of the mechanisms by which the immune system can respond to a streptococcal infection.