1-POM-2-2: White blood cells Flashcards
Outline the origin and functions of white blood cells, and recall common causes of abnormalities, including cancer.
What is the origin of white blood cells ?
multipotent haemopoietic stem cells give rise to a myeloblast which the gives rise to granulocytes and monocytes
what do Granulocytes refer to?
- neutrophils
2.Basophils
3.eosinophils
( these all have granules present in the cytoplasm that contain agents essential for their microbial function)
What is essential for the proliferation and survival of myeloid cells?
signalling through myeloid growth factors
Where does normal granulocyte maturation take place?
bone marrow
How long does a neutrophil granulocyte survive?
7-10 hours in circulation before migrating to tissues
What is the key physical characteristic of neutrophils?
nucleus of mature neutrophil is segmented (lobulated)
What is the main function of a neutrophil ?
defence against infection, it phagocytes and the kills micro-organism (bacteria), they also phagocytose cell debris helping recycle the tissues which are being broken down
What is the main function of eosinophils ?
defence against parasitic infections
they are also important in the regulation of type 1 hypersensitivity reactions ( they inactivate the histamine and leukotrienes released by basophils and mast cells)
What do the basophil granules contain?
stores of histamine
, heparin and proteolytic enzymes
what immune and inflammatory responses are Basophils involved in ?
- Mediation of the immediate-type hypersensitivity reaction in which IgE-coated basophils release histamine and leukotrienes
- Modulation of inflammatory responses by releasing heparin and proteases
- Mast cells are similar to basophils, but reside in tissues rather than the circulation
What are the key roles that Monocytes play ?
- phagocytosis of micro-organisms covered with antibody and complement
- Phagocytosis of bacteria/fungi
- antigen presentation to lymphoid and other immune cells
where do B lymphocytes originate form
in foetal liver and bone marrow
Where do lymphoid progenitors migrate from to, that leads to the development of T lymphocytes?
T cell development is initiated when immature progenitor cells migrate from the fetal liver or adult bone marrow to the thymus
What abnormalities can occur with white blood cells ?
- Transient leucocytosis= suggests a reactive cause and occurs when a healthy bone marrow responds to an external stimuli such as infection, inflammation or infraction (death of tissue resulting from a failure of blood supply)
- Persistent leucocytosis= suggests a primary blood cell disorder- the leucocyte count is abnormal due to acquired somatic DNA damaged affecting a haematopoietic precursor cell giving rise to blood cancers such as leukaemia, lymphoma, myeloma
what is leucocytosis?
to many white blood cells
what is leukopenia
a reduction in total number of white cells
neutropenia?
reduction in neutrophil count
lymphopenia ?
reduction in lymphocyte count
what is the most abundant leukocyte in the circulation
neutrophil hence it is more likely that leukocytosis/leukopenia is due to changes in the neutrophil count
what are some causes of neutrophilia ( too many neutrophils)
-infection, inflammation, infraction, other tissue damage
-may also occur during pregnancy, or after exercise, after administration of corticosteroids
why may exercise cause neutrophilia?
exercise causes rapid shift of neutrophils from the marginated pool to the circulating pool
what is myeloproliferative disorder (primary blood cancer) associated with ?
neutrophilia, basophilia and left shift
What is an examples of myeloproliferative disorders?
Chronic myeloid/ granulocyte leukaemia (CML)
what is neutrophilia accompanied by?
toxic changes and left shift
What is left shift ?
an increase in non-segmented neutrophils or that there are neutrophil precursors in the blood ( immature neutrophils)
When can neutropenia occur ?
- after chemotherapy, radiotherapy
- autoimmune disorders
- severe bacterial infections
- certain viral infections and drugs
- due to ethnicity
what are patients with very low neutropenia at risk for
they are at high risk of serious infections and at a higher risk of dyeing form sepsis
- they need urgent intravenous antibiotics
How many lobes should a normal neutrophil have
between 3 and 5 segments/lobes
What does Neutrophil hyper-segmentation mean ?
an increase in the average number of neutrophil lobes/segments (right shift)
when does right shift normally occur
due to a lack of vitamin B12 or folic acid
When do you normally see Eosinophilia
- allergy
- parasitic infection
- asthma
- eczema
- drugs
- some forms of leukaemia eg CML
When does basophilia take place
- leukaemia especially CML
when does Monocytosis (too many monocytes) take place ?
infection, chromic inflammation, some types of leukaemia
What are the causes of lymphocytosis
viral infection (transient)
lymphoproliferative disorder e.g chronic lymphocytic leukaemia
What are the causes of lymphopenia
- HIV infection
- Chemotherapy
- Radiotherapy
- Corticosteroids
What is leukaemia?
- cancer of the white blood cells
- they can either be myeloid or lymphoid depending on if the mutation in the bone marrow is in a myeloid or lymphoid progenitor
- leukaemic cells replace normal haempoietic cells in the bone marrow
