WEEK III (Role of white blood cells) Flashcards
What is the standard platelet count?
150-400 K/uL
What is the standard Lymphocyte % in the blood?
26.0-46.0 %
What is the standard White blood cell count and Red blood cell count?
WBC = 4.0-11.0 K/uL
RBC = 4.40-6.00 M/uL
What is the standard Haemoglobin count in the blood?
13.5-18.0 g/dL
What are Leukocytes/White blood cells?
The mobile units of the body’s immune defence system
Define Immunity
The body’s ability to resist or eliminate potentially harmful foreign materials or abnormal cells
What makes up the immune system?
Leukocytes and their derivatives & a variety of plasma proteins
What is the immune system?
An internal defence system that recognises and either destroys or neutralises materials that are foreign to the “normal self”
What are the functions of the immune system?
- Defends against invading disease-producing microorganisms
- Removes worn out cells and debris which paves the way for wound healing and tissue repair
- Identifies and destroys cancer cells that arise in the body
What are the properties of leukocytes?
- Go out to sites of invasion or tissue damage
- Located in the blood for rapid transport from their site of production or storage to wherever they are needed
- Widely dispersed
- Can defend in any location
What differentiates leukocytes from erythrocytes?
Leukocytes are able to exit the blood by assuming AMOEBALIKE behaviour to wriggle through narrow capillary pores and crawl to assaulted areas
What are the properties of Leukocytes?
- Lack haemoglobin so are colourless
- Vary in structure, function and number
- Larger than Red blood cells
What are the five different types of Leukocytes?
- Neutrophils
- Eosinophils
- Basophils
- Monocytes
- Lymphocytes
What categorises leukocytes into Granulocytes or Agranulocytes?
- Appearance of their nuclei
- Presence or absence of granules in their cytoplasm
Which Leukocytes fall into Polymorphonuclear granulocytes?
- Neutrophils
- Eosinophils
- Basophils
What are the properties of Polymorphonuclear granulocytes?
- Nuclei are segmented into several lobes of varying shapes
- Cytoplasm contains an abundance of membrane-enclosed granules
- Granules contain preformed, stored chemicals that are released by exocytosis when stimulated
How are the three different types of Granulocytes set apart?
On the basis of the varying affinity of their granules for dyes
EOSINOPHILS -> affinity for RED DYE eosin
BASOPHILS -> basic BLUE DYE
Neutrophils -> Neutral -> Show no dye preference
Which leukocytes fall into Mononuclear Agranulocytes?
Monocytes & Lymphocytes
What are the properties of Mononuclear Agranulocytes?
- Single, large, non-segmented nucleus
- Few granules
- MONOCYTES = larger of the two & oval/kidney shaped nucleus
- LYMPHOCYTES = smaller of the two & large, spherical nucleus
What are the functions of Neutrophils?
- Engulf and destroy bacteria intracellularly
- Neutrophil granules containing ANTIMICROBIAL PROTEINS fuse with invading bacteria ingested by PHAGOCYTOSIS and kill them inside the cell
- Release bacteria-killing chemicals into the ECF by exocytosis (DEGRANULATION)
- Programmed cell death (NETosis) which they kill nearby bacteria
What happens during NETosis?
Neutrophils use vital cellular materials to prepare a web of fibers called NEUTROPHIL EXTRACELLULAR TRAPS (NETs) which release into the ECF on their death -> fibers consist of CHROMATIN from the neutrophil’s nucleus studded with antimicrobial proteins from its cytoplasmic granules -> NETs bind with bacteria, trapping then destroying these foreign invaders extracellularly
An increase in circulating neutrophils (NEUTROPHILIA) accompanies which type of infection?
Acute Bacterial Infection
[This is why a DIFFERENTIAL WBC COUNT can be used to predict whether an infection is of bacterial or viral origin]
What makes a differential WBC count clinically appropriate?
Culturing a sample of the infected tissue’s fluid for a definite answer takes several days -> Differential WBC count -> Elevated Neutrophil count is highly indicative of bacterial infection -> Antibiotic therapy can be initiated long before the causative agent is known
An increase in Eosinophils (EOSINOPHILIA) is associated with what?
Allergic reaction & Internal parasitic infections
How do Eosinophils attack parasitic worms?
Attach to the worm and secrete substances that kill it
What are the properties of Basophils?
- Least numerous of leukocytes
- Similar structurally and functionally to mast cells
- Never circulate in blood but are dispersed in connective tissue
- Synthesise and store Histamine and Heparin
What is the function of Histamine?
Important in allergic reactions
What is the function of Heparin?
- Speeds up removal of fat particles from the blood
- Plays a role in immune responses
- Prevents coagulation & used as a anticoagulant drug
What is the life cycle of a granulocyte?
Stays in the blood for less than a day before entering tissues -> survives another 3 to 4 days unless it dies in the line of duty
What is the function of Monocytes?
- Become large tissue phagocytes called MACROPHAGES
- Performs phagocytosis
Describe the life cycle of a Monocyte
Emerge from bone marrow while still immature and circulate for only A DAY OR TWO before settling down in various tissues throughout the body -> Continue to enlarge and mature becoming MACROPHAGES -> Life span ranges from months to years unless it dies while performing PHAGOCYTOSIS
What is the function of Lymphocytes?
Provide immune defence against targets for which they are specifically programmed
What are the two different types of Lymphocytes?
- B LYMPHOCYTES = produce antibodies which circulate in the blood and are responsible for antibody-mediated/humeral immunity
- T LYMPHOCYTES = directly destroy their specific target cells by releasing chemicals that punch holes in the victim cell (CELL-MEDIATED IMMUNITY)
Describe the life cycle of a Lymphocyte
- Lymphocytes live for about 100-300 days
- Only a small amount of total lymphocytes are in transit in the blood at any given moment
- Most continually recycle among the BLOOD, LYMPH and LYMPHOID TISSUES spending a few hours in the blood
What are Lymphoid tissues?
Lymphocyte containing tissues such as lymph nodes and tonsils
Describe the Antibody
- Antigen binding site
- Constant region
- Variable region
- Heavy chain
- Light chain
- Disulphide bridge
What do all leukocytes, erythrocytes and platelets come from?
Undifferentiated pluripotent stem cells
What happens to pluripotent stem cells destined to become WBCs?
They eventually differentiate into various committed cells lines and proliferate under the influence of appropriate stimulating factors
Where are Granulocytes & Monocytes produced?
Only in bone marrow which releases these mature leukocytes into the blood
Where are Lymphocytes produced?
Originally from precursor cells in the bone marrow but most new ones come from LYMPHOCYTE COLONIES already in LYMPHOID TISSUES originally populated by cells derived from bone marrow
What is the least numerous of all blood cells?
Leukocytes
[not because fewer are produced but because they are merely in transit while in the blood]
What controls the rates of production of the various WBCs?
Chemical messengers arising from invaded or damaged tissues or from activated leukocytes themselves
What is a lab-produced messenger that directs the differentiation and proliferation of each cell type?
Granulocyte colony-stimulating factor
What are the properties of Granulocyte colony-stimulating factor?
- Stimulates increased replication and release of granulocytes from bone marrow
- Increases immune defence
- Decreases the incidence of infection in cancer patients treated with chemotherapy
- Suppress all rapidly dividing cells (hematopoietic cells, cancer cells)
What is the body’s only defence still available when bone marrow fails?
The immune capabilities of the lymphocytes produced by lymphoid tissues
What is Leukemia?
A cancerous condition involving uncontrolled proliferation of white blood cells
What are the consequences of Leukemia?
- Very high WBC count but most are ABNORMAL or IMMATURE so cannot perform their normal defence functions
- Displacement of other blood cell lines in bone marrow -> Reduced ERYTHROPOIESIS and INTERNAL BLEEDING because of platelet deficit -> Anemia
What are the properties of Monocytes?
- Found in blood
- Differentiate into macrophages
- Large, kidney shaped nucleus
- Extensive “frosted glass” cytoplasm
What are the properties of Macrophages?
- Antigen-presenting cell
- Phagocytose bacteria, cellular debris & senscent RBCs
- Differentiate from circulating blood monocytes
- Engage in antibody-dependent cellular cytotoxicity
- Important cellular component of granulomas where they may fuse to form giant cells
- Activated by IFN-gamma
What are the properties of Eosinophils?
- Defend against helminthic infections
- Bilobate nucleus
- Packed with large eosinophilic granules of uniform size
- Highly phagocytic for antigen-antibody complexes
- Produce histamines
What are the causes of Eosinophilia?
- Parasites
- Asthma
- Chronic adrenal insufficiency
- Myeloproliferative disorders
- Allergic processes
- Neoplasia
- Eosinophilic granulomatosis with polyangiitis
[PACMAN Eats]
What are the properties of Basophils?
- Mediate allergic reactions
- Densely basophilic granules (heparin and histamine)
- Leukotrienes synthesised and released on demand
What are the properties of Mast Cells?
- Mediate local tissue allergic reactions
- Contain basophilic granules
- Activated by tissue trauma
- Originate from the same precursor as basophils but are not the same cell type
Describe Mastocytosis
- A rare proliferation of mast cells in skin and/or extracutaneous organs
- Associated with c-KIT mutations and increase serum tryptase
