A 62-year-old man has a red, warm, painful lesion on his skin that

extends across his calf from the popliteal fossa to the ankle. This condition

is diagnosed as cellulitis, a bacterial infection of the deeper layers of the

skin. The red colour, increased temperature, and pain of the affected area are

due to an inflammatory response to the infection. In the patient, this

inflammatory reaction is largely caused by the release of pro-inflammatory

substances from the cells of the immune system, which are abundant in the

connective tissue. Which of the following cell types are involved?