white cells Flashcards
what cells are derived from common myeloid progenitors?
myeloid cells- i.e. not lymphocytes
megakaryocytes, erythrocytes, mast cells, myeloblasts
what do myeloblasts differentiate into?
granulocytes
basophils, neutrophils, eosinophils, monocytes
What is a band form?
Left shift neutrophil
In which granulocyte progenitors does cell division occur?
myeloblasts, promyelocytes, myelocytes
in which granulocytes does cell division not occur
metamyelocytes or band forms
what is the main function of the neutrophil?
phagocytosis and killing of micro organisms
what is chemotaxis?
first step in neutrophil migration to tissues
neutrophils become marginated in the vessel lumen and adhere to the endothelium and migrate into tissues
what happens after cytokine priming to neutrophils?
phagocytosis
what is the eosinophil’s main function?
defence against parasitic infection, also important in regulation of hypersensitivity reactions (inactivate histamine and leukotrienes released by basophils and mast cells)
they also do all neutrophil functions
what do basophils do?
release histamine and leukotrienes in the mediation of immediate-type hypersensitivity reactions when coated with IgE
modulate inflammatory responses by releasing heparin and proteases
what do the granules of a basophil store?
histamine, heparin and proteolytic enzymes
what are mast cells?
similar to basophils but reside in tissues rather than circulation
what is the monocyte’s function
phagocytosis of micro-organisms covered with antibody and complement
phagocytosis of bacteria and fungi (Fc mediated)
antigen presentation to lymphoid and other immune cells
what is another role of macrophages?
they can store and release iron
what cells are derived from the common lymphoid progenitor?
natural killer cells, small lymphocytes
where do B lymphocytes originate?
fetal liver and bone marrow
what does subsequent B cell maturation require?
exposure to antigens in lymphoid tissue, eg lymph nodes
where do T lymphocytes come from?
migrate from foetal liver to the thymus
what do natural killer (NK) cells do?
kill tumour cells and virus infected cells
what does transient leukocytosis suggest?
Reactive/secondary cause
occurs when normal/healthy bone marrow responds to an external stimulus (e.g. infection/ inflammation/ infarction)
what does persistent leukocytosis suggest?
Primary blood cell disorder
leukocyte count abnormal due to acquired somatic DNA damage affecting a haematopoietic precursor cell giving rise to blood cancer
which cell count does leukocytosis and leukopenia result from usually?
changes in the neutrophil count since it is the most abundant leukocyte in circulation
causes of neutrophilia
infection (usually bacterial), inflammation, infarction or other tissue damage
normal feature in pregnancy, could be seen following exercise and after the administration of corticosteroids
what other abnormalities in the blood film could neutrophilia be accompanied by?
toxic changes and left shift- early myeloid cells e.g. metamyelocytes being present in the blood
what is toxic granulation of neutrophils?
heavy, coarse granulation of neutrophils
what is CML
myeloproliferative disorder
primary blood cancer associated with neutrophilia, basophilia and left shift
what is left shift
an increase in non-segmented neutrophils/ there are neutrophil precursors in the blood
causes of neutropenia
chemo/radiotherapy
autoimmune disorders, severe bacterial infections
viral infections, drugs
sometimes could be physiological (e.g. benign ethnic neutropenia in people with African/Afro-Caribbean ancestry)
how many lobes should a normal neutrophil nucleus have?
3 to 5
what is neutrophil hypersegmentation (right shift)
caused by
megaloblastic anaemia (vit b12 or folic acid deficiency)
what is the usual cause of eosinophilia?
allergy/ parasitic infection, asthma, eczema, drugs
can occur in CML and other forms of leukaemia
what is the usual cause of basophilia?
usually due to leukaemia
cause of monocytosis
infection (particularly chronic bacterial infection)
chronic inflammation
some times of leukaemia
causes of lymphocytosis?
response to viral infection (transient)
lymphoproliferative disorder e.g. CLL (persistent)
what is the lymphocyte count threshold for lymphopenia?
< 1 x 10 ^9 /L
important causes of lymphopenia
HIV infection
chemotherapy
radiotherapy
corticosteroids
severe infection could develop transient lymphopenia
why does leukaemia occur
somatic mutations occurring in primitive cell which has a growth/ survival advantage over normal cells
mutations give rise to a clone which replaces normal cells
mutations may mean cell may not require usual growth factors, disturbance in proliferation/maturation, failure of apoptosis
mutations are in oncogenes or tumour suppressor genes
ALL characteristics
blasts- immature lymphoid cells
progenitors Aquire mutations, usually in genes encoding TFs
affects cells ability to mature but proliferation continues, leads to accumulation of blast cells
usually seen in childhood (results from somatic mutations in utero
CLL characteristics
mature lymphoid cells
steady expansion of clone cells which are functionally useless
replacement of normal cells by leukaemia clone
usually seen in the elderly
AML characteristics
myeloid blast cells
CML characteristics
mature myeloid cells
results from activation of signalling pathways by fusion protein BCR-ABL1
clinical features of leukaemia due to accumulation of abnormal cells?
leukocytosis
bone pain (if acute)
hepatomegaly
splenomegaly
lymphadenopathy (if lymphoid)
thymic enlargement (if T lymphoid)
skin infiltration
metabolic effects of leukaemic cell proliferation
hyperuricaemia and renal failure
weight loss
low grade fever
sweating
crowing out of normal haemopoiesis
fatigue, lethargy, pallor, breathlessness (caused by anaemia)
fever and other features of infection (neutropenia caused)
bruising, petechiae, bleeding (caused by thrombocytopenia)
when can a loss of normal immune function be observed in leukaemia?
when the patient has CLL
