White Blood Cells and WBC Disorders Flashcards
Erythrocytes
- Red blood cells
Leukocytes
- White blood cells
Thrombocytes
- Platelets
What percentage of body weight is blood?
- approx 7-8%
Blood cells
- heavier cells: bottom of tube
- haematocrit (packed cell volume) represents % to total blood volume occupied by RBCs
- normal haematocrit for men is 45%, women 42%
- WBCs and platelets found in buffy coat
- serum is clotted plasma
Types of white blood cells
- Monocyte
- Lymphocyte
- Eosinophil
- Basophil
- Neutrophil
Phagocytosis
- proteins on pathogen interacts with phagocyte receptors
- phagocyte envelops pathogen
- pathogen is digested
- pathogen breaks down into proteins and other molecules
Key features of Dendritic cells and macrophages
- phagocytic
- express receptors for apoptotic cells, DAMPs and PAMPs
- localize to tissues and T-cell zone of lymph nodes (DCs)
- express high levels of MHC class II molecules and antigen processing machinery
- express co-stimulatory molecules following activation
Key features of B cells
- internalize antigens via BCRs
- express MHC class II molecules and antigen processing machinery
- express co-stimulatory molecules following activation
Antigen recognition and effector functions of B cells
- antigen recognition: antigen on pathogens/soluble antigen
- effector functions: production of antibodies, neutralisation of pathogens, phagocytosis, complement activation
Antigen recognition and effector functions of helper T cell
- antigen recognition: antigen presented by professional APC
- effector functions: secretion of cytokines, macrophage activation, T cell and B cell activation, inflammation
Antigen recognition and effector functions of cytotoxic T cell
- antigen recognition: antigen presented by infected/malignant cells
- effector functions: elimination of infected/malignant cells
Antigen recognition and effector functions of regulatory T cell
- no antigen recognition function
- effector functions: regulate and/or suppress immune response
Antigen recognition and effector functions of natural killer cell
- antigen recognition: self-antigen/foreign antigen on host cells
- effector functions: elimination of infected/malignant cells
Innate immunity
- Non specific
- Requires no sensitising exposure
- No memory response
- Immediate/rapid response to threat
- First line of defense
- Includes physical barriers, chemical barriers, muco-ciliary escalator, phagocytes (neutrophils, monocytes and macrophages), NK cells, eosinophils, complement.
- Inflammation and fever responses
Adaptive immunity
- Involves lymphocytes (B&T cells)
- Humoral and Cell Mediated Immunity
- Specific.
- Exhibits memory (enhanced response on subsequent exposures from primary to secondary)
- Requires initial exposure to antigen, the sensitisation or priming step
- Cells have multiple copies of a single antigen specific receptor (SmIg or TCR).
- Antigens trigger clonal expansion of lymphocytes bearing appropriate receptor.
- ‘Selective’ rather than ‘Instructive’.
Immune cell origin
- Cells of the immune system are generated from haematopoietic stem cells in the bone marrow
- cells pass through different lineages of development and give rise to the different cells of the immune system
- All immune system cells are generated in bone marrow but T cells mature in the thymus
Bone marrow
- Inner spongy tissue of certain bones
- highly organized / regulated organ
- Site of haematopoiesis and fat deposition
Immune responses involving WBCs
- Defend against infection by viral, bacterial and parasitic pathogens.
- Identify and destroy cancer cells
- Remove injured, dead or dying cells and debris – essential for normal would healing and tissue repair.
- But can be involved in inflammatory or autoimmune diseases
Leukocytes
- WBC arise in bone marrow from single pluripotent stem cell.
- Various chemicals (colony stimulating factors) determine which specific cell type matures.
- Mature WBC circulate in peripheral blood so they can be transported to site of damage and/or invasion.
Leucocytosis (Leukophilia)
- high levels
- Due to infections, allergies, inflammatory diseases, cancer (blood cancers)
Leukopaenia
- low levels
- Due to bone marrow conditions (primary or secondary), certain drugs or treatments, certain infections (HIV), malnutrition, certain autoimmunity (Lupus/SLE)
Cells in innate immunity
- When protective barrier surrounding tissues is penetrated, a fast cellular response is needed to protect tissue from infection
- Do not recognise specific proteins/peptides related to one microorganism
- pattern recognition receptors (PRRs)
- recognise molecular patterns common to many invaders or self molecules which are seen when cells are damaged
Monocyte/macrophage
- Cytoplasm is agranular
- Largest WBC.
- Abundant light blue cytoplasm.
- U or kidney bean shaped nucleus – stains dark blue/purple
- arise from pluripotential stem cells within marrow
- After release from the marrow into circulation they form between 1-5% of circulating white cells
- After 24 hrs they migrate into the tissue and transform (differentiate) into tissue macrophages.
- Monocytes form blood borne phase of macrophages