Cells of Immunity

Question 1

Neutrophils

Answer 1

aka PMNs (polymorphonuclear cells)
Innate immunity
most numerous cellular component of innate immunity
responsible for phagocytosis and digestion of bacteria and particles
very populous in inflamed areas
multi-lobed nuclei, cytoplasmic granules (stain clear)
short life span (2d)
Differ in % of blood leukocytes

Question 2

Macrophages

Answer 2

Most important phagocytic cell
regulate homeostatic processes and help heal wounds
Mononuclear
Found in blood and all tissues (maturation depends on tissue factors)
Long lived (months) in certain tissues
Secrete pro-inflammatory cytokines
Present processed Ag to T cells
Phagocytosis and bacteria killing:
have Fc and complement receptors - only activate IR when encountered a pathogen via Fc receptor

Question 3

Eosinophils

Answer 3

Also a PMN
Present in low numbers
After release by bone marrow, migrate to and mature in spleen, then migrate to tissues
Phagocytosis and killing of parasites
Have Fc receptors on surface (bind Ab)
Bilobed nuclei, cytoplasmic granules (stain red)
Granules contain acid phophatase, peroxidase, toxic proteins
Life span: 12 days
Pro-inflammatory cells
Activated by: IL-3, IL5, GM-CSF, CXCL8

Question 4

Basophils

Answer 4

Also a PMN
Present in low numbers
multi-lobed nucleus, cytoplasmic granules (stain basophlic)
granules contain inflammatory molecules, including vasoactive amines: histamine, serotonin; cause vascular system to be leaky
not distributed in all tissues
Have special Fc receptor (FceRI) that helps play role in killing of parasites

Question 5

Mast Cells

Answer 5

Multi-lobed nucleus
Long-lived (weeks) after distributed into tissues
Distributed in tissues near blood vessels, primarily connective tissues and near body surfaces
Have FceRI receptor ==> play a role in killing parasites
Cytoplasmic granules contain inflammatory molecules, including vasoactive amines (histamine, serotonin)
Have Fc receptors that can bind to free Ab (w/o Ag)
Once activated, move to surface, and exude cytoplasmic components

Question 6

Dendritic Cells

Answer 6

Most important APC - provide a link between innate and adaptive immunity
Found in low numbers in tissues (skin epithelia, intestinal, respiratory, and reproductive mucosae)
Once activated by Ag/phagocytosis, they migrate to draining lymph nodes (==> they are MOBILE) and start adaptive IR

Question 7

Natural Killer Cells

Answer 7

Lymphocytic lineage
Possess different Ag receptors than B or T cells - doesn’t require thymus for maturation
Account for 15% of blood lymphocytes
Most are in secondary lymphoid organs
Kill tumor cells and virally infected cells (all are self cells infected by intracellular pathogens)
Have Fc receptor ==> present Ag too
Secrete IFN (activate other self cells to become antiviral)

Question 8

Lymphocytes

Answer 8

Arise from lymphoid progenitor in bone marrow/bursa
Leave bone marrow partially mature, and give rise to B and T lymphocytes
Small, round cells that can’t be differentiated visually
Mediate adaptive (Ag-specific) immunity
found in blood and lymphoid organs

Question 9

B-lymphocytes

Answer 9

Differentiate in bursa and bone marrow
Become memory cells or plasma cells that secrete Ab
Undergo clonal selection
Ag specific

Question 10

T-lymphocytes

Answer 10

differentiate in thymus
Can become CTLs (kill cells), or Helper T cells (activate cells to make IR)
Undergo clonal selection
Ag specific

Question 11

Cells of Innate Immunity

Answer 11

Neutrophils, Macrophages, Eosinophils, Basophils, Mast Cells, Dendritic Cells, Natural Killer Cells

Question 12

Cells of Adaptive Immunity

Answer 12

B lymphocytes, T lymphocytes