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BII > L7: White blood cells > Flashcards

L7: White blood cells Flashcards

1
Q

Leukocyte types

A

General function = defence against infection

Phagocytes:

  • Granulocytes - neutrophils (polymorphs), eosinophils, basophils
  • Monocytes

Lymphocytes: B and T cells, NK cells

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2
Q

Neutrophils

A

AKA polymorphs, PMNs, polymorphonuclear leucocyte, granulocytes

  • 90% of granulocytes, 75% of all leukocytes
  • Large 10-15um
  • Dense nucleus with 2-5 lobes, granules in cytoplasm
  • Normal WBC count 4-11x10^9/L
  • Neutrophils 2-7x10^9/L
  • Short lived in peripheral blood (10hrs)
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3
Q

Granulocyte kinetics

A
  • From marrow HSC –> myeloblast (later to granules, lobular nucleus)
  • 7-10 days maturation in marrow
  • Circulate 6-10 hours then into tissue to phagocytose
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4
Q

Regulation of granulopoiesis

A

Haematopoietic growth factors: IL3, stem cell factor, GM-CSF, G-CSF

G-CSF (granulocyte colony stimulating factor) in clinical use in NZ (filgrastrim) e.g. for patients receiving chemo to minimise neutropenia

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5
Q

Neutrophil function

A
  1. Chemotaxis: attracted to areas of foreign bodies/inflammation, migrate through endothelial wall into tissue
  2. Phagocytosis: foreign antigens (granules within neutrophils contains lysosomal enzymes)
  3. Killing of bacteria (oxidative and non-oxidative)
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6
Q

Clinical relevance of neutrophils

A
  • Neutrophil leucocytosis: inflammation/infection, may have left-shift (more immature forms in blood)
  • Neutropenia (low neutrophil count): idiopathic, drug effect, chemo –> at risk of infection (febrile neutropenia)
  • Neutrophil function defects (rare)
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7
Q

Monocytes

A
  • Large cell 15-20um
  • Central oval or indented nuclei
  • Blue-gray cytoplasm with granules
  • 0.2-0.8x10^9/L (less than 10% of total WBCs)
    Monoblast -> pro-monocyte -> monocyte
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8
Q

Monocyte kinetics

A
  1. Monocyte (haematopoietic derived) circulates for 1-3 days
  2. Enter tissues and transforms into macrophage
  3. Related cell throughout body: kupffer cells - liver, alveolar macrophages - lung, Langerhans cells - skin, microglial - brain
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9
Q

Monocyte/macrophage function

A

Mainly seen in chronic infections, intracellular parasites (e.g. TB)

  1. Phagocytosis
    - Chemotaxis
    - Opsonisation (receptors Fc and C3)
    - Phagocytosis and ingestion
    - Killing of ingested bacteria by fusion with monocytic lysosomal granules
  2. Synthetic function: complement, interferons, cytokines (TNF, IL1, GFs), prostaglandins
  3. Antigen presentation
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10
Q

Clinical relevance of monocytes

A

= Monocytosis

  • Reactive: chronic infection eg. TB, osteomyelitis
  • Malignant: acute myeloid leukaemia (monoblastic subtype), chronic myelomonocytic leukaemia (CMML)
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11
Q

Eosinophils + clinical relevance

A

Similar to neutrophils + similar maturation but much less and:

  • Bi-lobed nucleus
  • Red staining nucleus
  • 0-0.4x10^9/L

Clinical relevance = eosinophilia

  • Allergic or hypersensitivity reactions e.g. hayfever, asthma, drug reactions
  • Parasitic infestations (esp. gut-related)
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12
Q

Basophils + function

A
  • Infrequent cells in blood
  • Deep blue granules over bi-lobed nucleus
  • IgE binding sites
  • Related to mast cells
  • 0-0.1x10^9/L

Function:

  • Close relationship to mast cells
  • Granule: histamine, SRS-A, ECF-A
  • Type I hypersensitivity: degranulate
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13
Q

Lymphocytes

A
  • Small (10um diameter) mature cells
  • High nucleus:cytoplasm ratio
  • Condensed chromatin nucleus
  • Thin rim of agranular cytoplasm
  • 1.5-3.5x10^9/L

Circulating lymphocytes:
- 65-80% = T cells
- 5-15% = B cell
(B and T morphologically identical so identify by cell surface markers)
- NK cells (larger, cytoplasmic granules)

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14
Q

Lymphoid development

A

Blood stem cell –> lymphoid stem cell –> lymphoblast –> B lymphocyte, T lymphocyte, NK cell

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15
Q

Primary lymphoid organs

A

Lymphocytes are bone marrow derived but maturation in primary lymphoid organs

  • Bone marrow = B cells
  • Thymus = T cells
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16
Q

Secondary lymphoid organs

A
  • Lymph nodes
  • Spleen
  • Lymphoid tissue through body (gut, resp tract etc)
  • Bone marrow

Function = generation of adaptive immune responses

17
Q

Lymphadenopathy

A

= lymphoid enlargement
Reactive: e.g. viral infection, local bacterial infection
Malignant: e.g. of lymphoid tissue (lymphoma - B cell or T cell) or metastatic spread

18
Q

Lymphocytosis

A

= increase in lymphocytes
Reactive: viral infection e.g. infective mononucleosis
Malignant: e.g. chronic lymphocytic leukaemia

19
Q

Lymphopenia

A 
= low lymphocyte count
HIV infection (CD4 positive T helper cells lost)
- Profound T cell deficit)
- Opportunistic infection
- Malignancies

Others: congenital immune defects, steroid therapy, severe bone marrow failure

20
Q

Function of lymphcytes

A

B cell -> plasma cell (produce antibodies)

T cells = cell-mediated immunity

  • CD4 positive T helper cells
  • CD8 positive T cytotoxic cells

BII (41 decks)

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