block i: innate immune cells, origins, and functions

hematopoietic stem cell (HSC)

multipotent stem cell in the bone marrow that gives rise to blood and immune cells

two major immune-cell lineages

lymphoid lineage and myeloid lineage

common lymphoid progenitor (CLP)

gives rise to B cells, T cells, NK cells, and innate lymphoid cells

common myeloid progenitor (CMP)

gives rise to granulocytes, monocytes/macrophages, most dendritic cells, and mast cells

B cell

common lymphoid lineage, matures in bone marrow, responsible for humoral adaptive immunity

T cell

common lymphoid lineage, matures in thymus, responsible for cell-mediated adaptive immunity

NK cell

common lymphoid lineage, innate immune cell, kills infected or stressed cells without antigen-specific receptors

innate lymphoid cell (ILC)

common lymphoid lineage, rapidly produces cytokines, lacks antigen-specific receptors

neutrophil

myeloid lineage, rapidly recruited phagocyte, important against extracellular microbes

monocyte

myeloid lineage, circulates in blood, can enter tissues and differentiate into macrophages

macrophage

myeloid lineage, tissue phagocyte, recognizes microbes, phagocytoses microbes, produces inflammatory cytokines

dendritic cell

antigen-presenting cell that detects and ingests pathogens, processes antigen, activates T cells, bridges innate and adaptive immunity

eosinophil

myeloid granulocyte, important in parasite defense and allergic responses

basophil

myeloid granulocyte, releases inflammatory mediators, involved in allergic and parasite responses

mast cell

tissue-resident myeloid cell, releases inflammatory mediators, involved in allergy and parasite responses

granulocytes

neutrophils, eosinophils, basophils

major innate phagocytes

neutrophils and macrophages

first major leukocyte recruited during acute inflammation

neutrophil

circulating precursor that can become a macrophage

monocyte

cell that bridges innate and adaptive immunity

dendritic cell

innate cell important for early killing of virus-infected cells

NK cell

cell especially associated with parasite defense

eosinophil

major tissue-resident phagocyte

macrophage

ILC1

produces IFN-γ, associated with defense against viruses and intracellular pathogens

ILC2

produces IL-5 and IL-13, associated with parasite defense and tissue repair

ILC3

produces IL-17 and IL-22, associated with extracellular bacteria and barrier defense

NK cell effector molecules

perforin and granzymes