The function of chemical substances such as histamine and leukotrienes would be

The function of chemical substances such as histamine and leukotrienes would be to stimulate inflammation. Leukotrienes is an example of eicosanoids which play a key role in the pathogenesis of inflammation. They are synthesized in the leucocytes from arachidonic acid via the actions of 5-lipoxygenase. The release of histamine serves as an important part of the body's immune response; when the body comes into contact with an allergen, such as pollen or animal dander, histamine is released by the body to the site of contact and triggers inflammation. 

An autotrophic protist - they can perform photosynthesis and mainly consist of unicellular algae. they can be divided into number of systematic group according to the shape of their cell and the type of photosynthetic pigments they use.

No its just makes the straight guy curious