P: White blood cells & haemostasis Flashcards
1
Q
Innate response
A
general processes against infectious agents
2
Q
Adaptive response
A
directed response against specific infectious agents.
3
Q
Leukocytes
A
4-10 x 10^9 cells/L
Nucleated cells with 5 subtypes:
- Neutrophils (phagocytosis)
- Eosinophils (phagocytosis)
- Monocytes (phagocytosis)
- Basophils (released hydrolytic enzymes from cytoplasmic granules + histamine)
- Lymphocytes
4
Q
Granulocytes
A
- Neutrophils, eosinophils, basophils
- Granules visible in cytoplasm
- Called polymorphonuclear leukocytes. (PMN or PML)
- Multiple nuclei of varying shapes
- Originate from bone marrow precursor cells: myelocytes
5
Q
Genesis of myelocytes
A
- Under cytokine control
- 6-10 days in bone marrow/circulation
- 4-5 days in tissues
- Large numbers held in marrow as reserve pool
- Marrow has 10x as many myeloid cells as erythroid cells
- Neutrophils - most common white cell (40-75%)
- Eosinophils - 1-6% circulating cells
- Basophils - least common circulating cell (<1% in adult)
6
Q
Neutrophils
A
- Participate in phagocytosis in blood + tissues
- Circulate in blood and migrate into tissues by squeezing through pores via diapedesis
- Numbers increase dramatically during infection.
- Constitute about 50-80% of all leukocytes.
7
Q
Eosinophils
A
- Constitute 1-4% of all leukocytes
- Weakly phagocytic: mainly attack infecting parasites too large to be engulfed by attaching to parasite and secrete hydrolytic enzymes from cytoplasmic granules
- Can reverse tissue damage during allergic reactions: phagocytose allergen-antibody complexes & inflammation inducing substances.
8
Q
Basophils
A
- Least common circulating leukocyte <1%
- Non-phagocytic, act like eosinophils to release hydrolytic enzymes from cytoplasmic granules
- Release chemicals that contribute to allergic reactions: histamine, bradykinin, serotonin, heparin, slow-reacting substance of anaphylaxis, lysosomal enzymes.
9
Q
Monocytes
A
- Largest of leukocytes - 2-4%
- Circulate in blood for a few hours before migrating into tissues: increase in size by factor 5-10 and develop into tissue macrophages where they phagocytose infectious agents + abnormal/ dying cells including RBCs only in tissues.
10
Q
Monocyte –> macrophage cell system:
A
- Monocytes enter tissues + become macrophages
- Attach to tissues indefinitely + can be recruited into tissues if required
- Reticuloendothelial system
11
Q
Macrophages prominent in:
A
- Lymph nodes
- Lung alveolar walls
- Liver sinusoidal capillaries
- Red pulp of spleen
12
Q
Chemotaxis
A
Neutrophils & macrophages are recruited to tissue inflammation
13
Q
Inflammation
A
- Large number of neutrophils recruited by chemotaxis + enter by margination
- Activated macrophages secrete factors which promote granulocyte + monocyte production.
14
Q
Natural killer cells (innate immunity)
A
- Produced from lymphoid lineage
- Specifically target tumour cells + virus infected cells
- Induce programmed cell death (apoptosis) via release of contents of cytoplasmic granule
- Activated in response to interferons/ macrophage-derived cytokines.
15
Q
Lymphocytes (acquired immunity)
A
- 20-40% of leukocytes
- 3 main subtypes:
1. B lymphocytes: mature into plasma cells which secrete antibodies
2. T lymphocytes: helper T cells secrete cytokines which activate other leukocytes.
Cytotoxic T cells secrete factors that kill virus-infected cells + tumour cells
3. Natural killer cells: also secrete factors that kill virus-infected cells + tumour cells.