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Questions and Answers
What is the normal range of white blood cell (WBC) count in a liter of blood?
What is the normal range of white blood cell (WBC) count in a liter of blood?
Which type of white blood cell is primarily involved in specific immunity?
Which type of white blood cell is primarily involved in specific immunity?
What percentage of Eosinophils is typically found in a normal differential WBC count?
What percentage of Eosinophils is typically found in a normal differential WBC count?
Which process describes the movement and adhesion of neutrophils during inflammation?
Which process describes the movement and adhesion of neutrophils during inflammation?
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What condition is indicated by a white blood cell count of less than 1.5 × 10^9 /L?
What condition is indicated by a white blood cell count of less than 1.5 × 10^9 /L?
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What is the primary method by which the immune system destroys invading agents?
What is the primary method by which the immune system destroys invading agents?
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Which type of blood cell is primarily responsible for antibody formation?
Which type of blood cell is primarily responsible for antibody formation?
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Which of the following components of blood is considered a leukocyte?
Which of the following components of blood is considered a leukocyte?
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What describes the process of immune tolerance?
What describes the process of immune tolerance?
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What is the function of platelets in the bloodstream?
What is the function of platelets in the bloodstream?
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Study Notes
Blood Cells and Platelets
- Blood has four major elements: red blood cells (erythrocytes), white blood cells (leukocytes), platelets (thrombocytes), and plasma.
Objectives
- Define immunity and its mechanisms.
- Identify different types of granulocytes and their functions.
- Describe types and functions of lymphocytes.
- List common white blood cell (WBC) disorders.
- Define immune tolerance and autoimmune diseases.
- Describe the function of platelets (platelet plug formation).
- List types of platelet disorders.
White Blood Cells (WBCs)
- WBCs (leukocytes) protect the body from microbes.
- WBCs are mobile units of the body's protective mechanisms (immunity).
- Function of WBCs is to ingest and destroy microbes/antigens.
Immunity
- Immunity is composed of blood leukocytes (white blood cells) and tissue cells.
- Immunity works in two ways to prevent disease:
- Destroying invading agents (phagocytosis).
- Forming antibodies and sensitized lymphocytes, which destroy invaders
WBC Count
- Normal WBC count is 4000-11000/µL or (4-11 × 10⁹/L).
- Life span in bloodstream 4-8 hours.
- Tissue life span is estimated at 4-5 days.
WBC Types
- Granulocytes: neutrophils (50-70%), eosinophils (1-4%), basophils (0-2%).
- Agranulocytes: lymphocytes (20-40%), monocytes (2-8%).
Neutrophils
- Normal range: (50-70%) 1.5 - 10 × 10⁹/L.
- High count (neutrophilia): bacterial infection, tissue necrosis (e.g., myocardial infarction).
- Low count (neutropenia or agranulocytosis): < 1.5 × 10⁹/L.
Functions of Neutrophils
- Ingest and destroy invading microorganisms in tissues.
- Cause effective phagocytosis to kill foreign particles and microbes.
- Form a first line of defense.
- Play a central role in the early stages of acute inflammatory response to tissue injury.
- Major constituent of pus.
Functions of Eosinophils
- Absorb histamine released in allergic conditions.
- Detoxify toxins and foreign proteins.
- Weak phagocytes.
- Protect against parasitic diseases.
Functions of Basophils
- Least common WBCs.
- Large, intensely basophilic, cytoplasmic granules.
- Allergens trigger rapid exocytosis of granules, releasing histamine to cause allergic rhinitis, urticaria, and anaphylaxis.
- Secrete heparin (anticoagulant).
- Share common lineage with tissue mast cells, exhibiting structural and functional similarities.
- Have highly specific membrane receptors for IgE produced in response to allergens.
Monocytes
- Large, motile, phagocytic cells.
- Highly phagocytic (macrophages).
- Leave blood to connective tissues (diapedesis).
- Engulf bacteria.
- Repair tissue after inflammation.
Innate Immune System
- Barriers: epithelium, secretions, fluid flow.
- Cells: phagocytes (neutrophils, macrophages).
- Chemical signals: interferons, complement proteins.
- Nonspecific: works regardless of the invader.
Acquired/Adaptive Immune System
- Relies on B cells and T cells.
- Provides specific and delayed, robust immune responses.
B-Cells
- Formed and mature in bone marrow.
- Circulate through lymphatic system.
- Surface antigen-specific receptors (membrane-bound antibodies).
Plasma Cells
- Formed from B lymphocytes.
- Secrete immunoglobulins (antibodies).
- Crucial for humoral immunity.
T-Cells
- Migrate to thymus for maturation.
- Express T cell receptors (TCRs).
- Recognize foreign antigens presented by antigen-presenting cells (APCs).
- Trigger cell-mediated immunity.
Types of T Lymphocytes
- Helper T cells: activate T and B cells, and other immune cells
- Cytotoxic T cells: eliminate pathogens and infected cells.
- Regulatory T cells: distinguish between self and non-self, decreasing risk of autoimmune diseases.
Immunological Tolerance
- Unresponsiveness to an antigen induced by exposure of lymphocytes to that antigen during fetal life.
- Significance: prevents the immune system from attacking the body's own cells (self-tolerance); breakdown leads to autoimmunity.
Autoimmune Diseases
- Failure of the body's defense system to recognize its own constituent parts (self).
- Immune response targets self-cells and tissues.
- Disease resulting from an aberrant immune response.
Platelets (Thrombocytes)
- Small cell fragments from megakaryocytes.
- Crucial for haemostasis.
- Oval, granular, non-nucleated bodies (2-4µm in diameter)
- Short life span (8-12 days).
- Normal platelet count: 150-400 x 10⁹/L.
Platelet Functions (Haemostasis)
- Circulate in resting, inactive state.
- Must become activated.
- Adhere (stick) together - Aggregation.
- Platelet plug formation (adhesion to exposed collagen, activation by ADP and thrombin, release of granules).
- Role in phagocytosis (ingest certain particles, such as viruses).
Platelet Disorders
- Thrombocytopenia (very low platelet counts (<50,000/µL)).
- Idiopathic: unknown cause
- Secondary: associated with bone marrow aplasia (e.g., exposure to radiation).
- Thrombasthenia: defective platelet function (e.g., severe uremia, exposure to certain drugs).
Leukocytosis and Leukopenia
-
Leukocytosis: high WBC count (often due to bacterial inflammation, allergic or parasitic diseases.)
- Neutrophilia: bacterial infection
- Eosinophilia: allergic/parasitic diseases
- Basophilia: allergic diseases
- Lymphocytosis: viral/chronic bacterial
- Leukopenia: low WBC count (often due to bone marrow depression, splenomegaly, or autoimmune disorders)
Spleen Function
- Defense against parasites and microbes.
- Blood formation
- Removal of old blood cells
- Blood reservoir
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Description
This quiz covers the key aspects of blood cells, including the various types of blood cells—red, white, and platelets. It aims to enhance understanding of immunity, its mechanisms, and the role of different cells involved in defense against diseases. You'll also explore WBC disorders and platelet functions.
