2.1 White Cells in Health Flashcards
All types of blood cells (red, white, platelets) originate from multipotent haematopoietic stem cells in the bone marrow:
• Give rise to committed lymphoid stem cells (______________) and committed myeloid stem cells (______________________)
• Committed myeloid stem cells give rise to myeloblasts, which in turn differentiates into granulocytes or monocytes (with cytokines __________________)
o Cytokines are clinically important as G-CSF is often used to _________________
• Wider range of cells in the bone marrow (BM) than peripheral blood (PB) → PB contains more _______________________
B cells, T cells, NK cells;
RBCs, granulocytes, megakaryocytes, monocytes;
G-CSF, M-CSF, GM-CSF;
stimulate neutrophil recovery post-chemotherapy;
mature lymphocytes (T cells, B cells, NK cells) and phagocytes (granulocytes and monocytes)
WHITE CELL MORPHOLOGY
White blood cells (leukocytes) can be distinguished based on morphology, anatomical position (site where they are found), or cell surface antigens:
1) Myeloblast: Earliest recognisable form with large nucleus and prominent nucleoli (__________ in the nucleus) and ___________ cytoplasm (high _______)
2) Promyelocyte: _______________ begin to develop
3) Myelocyte: Smaller nucleus with more cytoplasm (clearly seen granules)
4) Metamyelocyte: ______ nucleus (lack of nucleoli) and cytoplasmic granules
5) Band form: Nucleus begins to segment; band form does not divide (differentiates further into a neutrophil)
6) Neutrophil: Characteristic segmented nucleus with bluish granular cytoplasm
* All the precursors (except neutrophils) are only found in the bone marrow (not PB), and _____________ may also give rise to other granulocytes (basophils and eosinophils).
pale areas; scanty bluish; N:C ratio;
Bluish cytoplasmic granules;
Bent;
myeloblasts
Neutrophils
- found in the ________________
- survives 7-10 hours in the circulation before migrating into tissues
- multi segmented nucleus with bluish granular cytoplasm
- mainly for defence against ________ (via phagocytosis and digestion → cytoplasmic debris)
bone marrow, peripheral blood, tissues
Neutrophilia: 50% of circulating neutrophils are found in a ______________________ (sticking to the sides and not counted in PB. May be released (e.g. during _______________) to cause neutrophilia → not due to increased neutrophil production but rather the release of the marginating pool.
marginating pool in blood vessels;
steroid administration)
Eosinophils
- found in peripheral blood and tissues
- spnd less time in the circulation than neutrophils
- ______ colour (from reddish granules) and _____ nucleus
- mainly for defence against ______________
Brighter pink;
bilobed
parasitic infections
Basophils
- Very few in number (_____) in the peripheral blood
- Normally do not migrate into tissues (unless during hypersensitivity)
- _______________ across the bilobed nucleus (hard to see on LM)
- Mainly involved in allergic reactions
0.5%;
Very dark granules densely overlaid
Monocytes
- larger size, ____ shaped nucleus
- Spend few days in circulation before entering tissues and develop into macrophages and other specialised cells (phagocytic and scavenging functions)
- Macrophages also ___________________
kidney bean shaped;
store and release iron
Lymphocytes
- large cells with ______
- Recirculate to lymph nodes and other tissues (spleen and bone marrow) then back to the bloodstream (very variable __________________)
round nucleus;
intravascular lifespan
[LYMPHORETICULAR SYSTEM]
Lymphoid stem cells differentiate into T cells (develop in thymus), B cells (develop in bone marrow), and NK cells (cytotoxic cells lacking __________):
• B cells and T cells, immature and mature lymphocytes, and myeloblasts and lymphoblasts are difficult to distinguish as they appear morphologically similar
• B and T cells occupy different anatomical positions within the lymphoreticular system (possessing different types of tissues) which may be used to identify them:
Generative
- Bone marrow, thymus
- Generation/ maturation of ______________
Reactive
- Lymph nodes, spleen
- Development of general immune reaction
Acquired
- ________________ (e.g. skin, stomach, lungs)
- Development of local immune reaction
TCRs;
lymphoid cells;
Extranodal lymphoid tissues;
The cortex of lymph nodes possesses B cell areas and T cell areas (observed on histology):
B cells: Germinal centres (round purple area) contain B lymphocytes, _____________, and is the site where B lymphocytes which bind ___________ are selected and activated
• Mantle zone (darker zone surrounding germinal centre) contains _______________
T cells: Paracortex (outside of the mantle zone) contains T lymphocytes, interdigitating dendritic cells and ________, and is the site where T lymphocytes which bind antigen epitopes are selected and activated
dendritic cells;
antigen epitopes;
naïve unstimulated B lymphocytes;
HEVs
SURFACE ANTIGEN PROFILE
All cells have a characteristic antigen profile (CD markers) on their cell surface which can be detected by labelled antibodies:
• Identifies the cell type and degree of maturation
• Principle of using antibodies to identify cell surface antigens is used in both immunohistochemistry and flow cytometry
• Important markers: CD3 (T cells), CD20 (B cells)
TdT is seen in ______
Immunohistochemistry
- used to identify proteins on the cell surface or in the cytoplasm
- use cells fixed on __________
- labelled antibodies to cell surface receptors visible ___________
Flow cytometry
- used to identify proteins on the cell surface or in the cytoplasm
- using __________
- fluorochrome labelled antibodies detected via ________________
Lymphoid stem cell;
tissue sections;
LM;
cell suspensions;
laser sources of different wavelengths
Healthy white cells respond to infections and systemic diseases (e.g. cancer, autoimmune diseases, metabolic disorders):
• Quantitative changes: increase or decrease in number
• Qualitative changes: ________________ (in neutrophils), reactive/atypical lymphocytes, less mature cells seen in circulation like ______________ (e.g. metamyelocytes, immature RBCs)
toxic granulation;
non-segmented granulocytes
A left shift refers to an increase in _________________ (band forms, myelocytes, promyelocytes) or the presence of neutrophil precursors in the blood (usually not present):
• Leucoerythroblastic film: early WBC and RBC precursors found in the ______ (evidence of left shift)
non-segmented neutrophils;
PB
Atypical lymphocytes are found in response to certain viral infections (e.g. infectious mononucleosis/glandular fever):
• Appear as __________________ that have a substantial amount of cytoplasm (stained very pale → difficult to see) → distinguishes it from blasts
large cells which skirt around the RBCs
Toxic granulation refers to the _______________ with the presence of cytoplasmic vacuoles:
• Occurs due to infections, inflammation and tissue necrosis
• May also be a normal feature of _________
heavy granulation of neutrophils;
pregnancy
