Table 4.

Overview of the defining features of innate and adaptive immunity [1]

	Innate immune system	Adaptive immune system
Cells	Hematopoietic cells: • Macrophages • Monocytes • Dendritic cells • Mast cells • Neutrophils • Basophils • Eosinophils • NK cells Non-hematopoietic cells: • Epithelial cells (skin, airways, gastrointestinal tract) • Endothelial cells	Hematopoietic cells: • T cells • B cells Dendritic cells (APCs)
Molecules	• Cytokines • Complement • Proteins and glycoprotein	• Antibodies (Ig) • Cytokines
Response time	• Immediate	• Delayed by hours to days
Immunologic memory	• None: responses are the same with each exposure	• Responsiveness enhanced by repeated antigen exposure