White cells Flashcards
1
Q
What do white cells include?
A
- White cells comprise granulocytes, monocytes and lymphocytes
- Granulocytes refers to neutrophils, basophils and eosinophils which all have granules present in the cytoplasm containing agents essential for their phagocytic function and killing of the phagocsed micro-organisms
- Monocytes are the precursor of tissue macrophages
2
Q
Where are white cells derived from?
A
- Granulocytes and monocytes are derived from myeloid progenitor stem cells
- The synthesis of granulises and macrogphased is controlled by growth factors such as Granulocyte-colony stimulating factor (G-CSF) and Granulocyte-macrophage colony stimulating factor (GM-CSF)
3
Q
When does cell division occur and not occur?
A
- Cell division occurs in myeloblasts, promyelocytes, myelocytes
- Does not occur in metamyelocytes or band forms
4
Q
What is a neutrophil?
A
- Neutrophil granulocyte survives 7-10 hours in the circulation before migrating to tissues
- The nucleus of the mature neutrophil is segmented (sometimes referred to as lobulated)
- Its main function is defence against infection; it phagocytes and then kill micro-organisms
- The first step in neutrophil migration to tissues is chemotaxis
- Neutrophils become marinated in the vessel lumen, adhere to the endothelium and migrate into tissues
- Phagocytosis of micro-organisms occurs following cytokine priming
5
Q
What is the eosinphil?
A
- A myeloblast can also give rise to eosinophil granulocytes
- The eosinophil spends less time in the circulation than does the neutrophil
- Its main function is defence against parasitic infection
6
Q
What is the basophil?
A
- Myeloblast give rise to basophil granulocytes
- Its granuloes contains stores of histamine and heparin as well as proteolytic enzymes
- Basophils are involved in a variety of immune and inflammatory responses
7
Q
What is the monocyte?
A
- The myeloid stem cell can also give rise to monocyte precursors and hence monocytes
- Moncoytes spend several days in the circulation
- Monocytes present antigens to lymphoid cells
- Monocytes migrate to tissues where they develop into macrophages (also known as histiocytes) and other specialised cells that have a phagocytic and scavenging function
- Macrophages also sort and release iron
8
Q
Describe the origin of white cells
A
- The multipoint haemopoietic stem cell also gives rise to a lymphoid stem cell
- The lymphoid stem cell gives rise to T cells, B cells and natural killer (NK) cells
- Lymphocytes recirculate to lymph nodes and other tissues and then back to the blood stream
- Intravascular life span is very variable
- B lymphocytes mature into plasma cells which produce antibodies
- T lymphocytes are involved in cell-mediated immunity
- NK cells are part of the innate immune system - they can kill tumour cells and virus-infected cells
- Not all lymphocytes look the same
9
Q
What are some examples of leucocytosis?
A
Neutrophilia Lymphocytosis Monocytosis Eosinophilia Basophilia
10
Q
What are some examples leucopenia?
A
Neutropenia: reduction in neutrophil count
Lymphophenia: reduction in lymphocyte count
11
Q
Describe neutrophilia
A
Neutrophilia: too many neutrophils
- Causes: infection (particularly bacterial infection), inflammation, infraction or other tissue damage, myeloprpliferative neoplasms (chronic myeloid leukaemia _
- Neutrophilia is also a normal feature in pregnancy and may be seen following exercise (caused by a rapid shift of neutrophils from the marginated pool to the circulating pool) and after administration of corticosteroids
- Neutrophilia may be accompanied by toxic changes and left shift (left shift means there is an increase in non-segmented neutrophils or that there are neutrophil precursors in the blood)
- Toxic granulation is heavy coarse granulation of neutrophils (it can be a feature of pregnancy
12
Q
Describe neutropenia
A
- Neutropenia can occur in a large number of conditions
- This includes following chemotherapy and radiotherapy
- Neutropenia can also result from autoimmune disorders severe bacterial infections, certain viral infections and drugs, e.g. some anticonvulsant and antipsychotic drugs and some antimalarials
- Sometime, neutropenia has a physiological basis e.g. benign ethnic neutropenia in people of African or Afro-Caribbean ancestry
- Patient with very low neutrophil counts (<0..5 x 10^9/l) are at a high risk of serious infection and the need urgent treatment with intravenous antibiotics
13
Q
Describe lymphocytosis
A
- Often response to viral infection (transient) (often ‘atypical lymphocytes)
- Can result from leukaemia (persistent)
14
Q
Describe lymphopenia
A
- Refers to a decrease in number of circulating lymphocytes
- Defined as a total lymphocytes count < 1x10^9 / l
In normal blood most lymphocytes are CD4+ T cells - Causes of lymphopenia: HIV infection, chemotherapy, radiotherapy, corticosteroids
- Patients with severe infection may develop a transient low lymphocytes count
15
Q
What is the hyperhsegmented neutrophil?
A
- A normal neutrophil should have between 3 and 5 segment or lobes
- Neutrophil hypersegemenrtation means there is an increase in the average number of neutrophil lobes or segments
- Usually results from a lack of Vitamin B12 or folic acid (megaloblastic anaemia)
