leukocytes Flashcards
where are leukocytes found and functions?
complete colourless cells found in marrow, blood and lymph
functions include :
* fight against infection
* participate in immune responses
* remove old cells, debris and foreign objects
leukocytes can be classified into 2 groups. what are they?
granulocytes
* granules in cytoplasm can be seen when stained
* have lobulated nuclei called polymorphs
* functions in tissues rather than in blood
agranulocytes
* have some granules but not easily visible
how long on avg do neutrophils spend in circulating blood?
7 hours
neutrophil morphology
- 10-14 µm in diameter
- lobes connected by chromatin threads
- multilobed
- small granules which stain lilac
- granules contain range of enzymes and antimicrobial proteins
roles of neutrophils
- primary defense against bacteria, virus, fungus
- migrate to sites of infection
- respond to chemotactic stimuli
- rolling, adhering and diapedesis
- phagocytosis
- component of inflammation - release leukotrienes, prostaglandins
- febrile response - release an endogenous pyrogen
neutrophils - phagocytosis process
when do neutrophils increase? - physiological increases
- after exercise
- after meals
- pregnancy, menstruation
- mental stress
- after injection with adrenaline
when do neutrophils increase? - pathological increases
- after pus-forming bacterial infections
- acute rheumatic fever
- gout
- tisssue destruction : burns, haemorrhage, myocardial infarction
what is neutropenia and what can cause this?
low levels of neutrophils caused by :
* being a child
* typhoid fever
* viral infections
* malaria
* aplasia of bone marrow
* bone marrow depression
size of eosinophils
10-14 µm in diameter
functions of eosinophils
- defence against parasitic infection
- attack bacteria, but not as effective as neutrophils
- phagocytic but less motile than neutrophils
morphology of eoisinophils
- acidophillic, appear light pink after staining
- granules are bright brick red colour from eosin dye
- granules contain lysozymes and high histamine content
what is eosinophilia? and causes
increased number of eosinophils due to :
* allergic conditions e.g. asthma, hay fever
* parasitic infections
* skin disease
what is eosinopenia? and causes
reduced number of eosinophils due to :
* steroid therapy
* stressfull situations
* acute pyogenic infections
size of basophils
10 – 14 µm in diameter
functions of basophils
main role is in allergic reactions
* release histamine
* release serotonin + others causing local vascular and tissure reactions
* prevents spread of allergic inflammatory process
* liberate heparin, which acts as an anticiaguland keeps blood flowing
mildly phagocytic but don’t attack parasites
basophillia causes
- viral infections
- allergic disease
- chronic myeloid leukaemia
basopenia
- steroids
- drug induced reactions
- acute pyogenic infections
what are mast cells?
- large cells resemble basophils
- play role in allergic reactions
- present in bone marrow
- abundant beneath epithelial surfaces
- remain in connective tissue
size of monocytes
18 – 20 µm in diameter
what is a monocyte?
- single nucleus which is indented
- lots of clear cytoplasm
- no visible granules
- stains pale blue
monocytes mature into…
macrophages or histocytes which phagocytose microbes
monocytes presents ____ to ____
monocytes present antigens to lymphocytes
monocytes crucial fighters against what kind of ingections?
chronic bacterial infections + chronic fungal infections
roles of monocytes
- secrete cytokines which enhance inflammatory response
- secret growth factors - promote production of neutrophils
- remove parasites (malarial)
- destroy RBCs at end of their life span
- store released iron
- kill tumour cells
- synthesise complement, clotting factors, proteases
monocytosis causes
- bacterial infections e.g. TB
- viral infections
- protozoal infections
monocytopenia
- very rare
- could be due to hypoplastic bone marrow
size of lymphocytes
7 – 10 µm
types of lymphocytes
B cells + T cells
B cells roles
humoral immunity
T cells roles
cellular immunity
lymphocytosis - physiological causes
- healthy young children
- during menstruation
lymphocytosis - pathological causes
- chronic infections
- lymphatic leukaemia
- viral infections
- autoimmune diseases
lymphocytopenia causes
- steroud and immunosuppressive therapy
- hypoplastic bone marrow
- HIV
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