A leukocyte is a white blood cell (WBC). There are MANY different types of leukocytes that do many different things. Neutrophils, eosinophils, basophils, lymphocytes and monocytes, each responsible for a different process, whether that be fighting off bacteria, reducing cellular signalling via certain enzymes and hormones.
Are the first cell to ever respond to an injury or injurious agent. What a neutrophil does is hunt down this injury or injurious agent and coats any microbe/bacteria in an enzyme that signals to cells to perform phagocytosis on this particular particle. What neutrophils also produce is oxygen radicals, bactericidal and produce cytokines.
These WBC appear at the site of injury between 48-72hours post injury. They are bactericidal, meaning they fight off any microbes of bacteria within the site of injury. These particular WBC's however, play a crucial role in a parasitic defence within the site of injury; they release a destructive enzyme that slowly weakens and breaks down the parasite. This cells is particularly prominent in allergic reactions!
These cells are baby mast cells. They contain little granules of histamine to be released at the site of injury.
Is a component of connective tissue - which is what the dermis of the skin is made up of. These cells contain hormones like histamine, serotonin, heparin and bradykinin.
Are extremely bactericidal so they are largely responsible for reducing bacteria, damaged cells and waste from the site of injury, as well as the production of cytokines.