White Cells - Leukocytes Flashcards
White cells are comprised of which 3 parts?
Granulocytes, monocytes and lymphocytes
What are granulocytes and their function?
Consists of neutrophils, basophils and eosinophils, all have granules present in the cytoplasm containing agents to breakdown phagocytosed micro-organisms
What are monocytes?
Precursors (substance from which another is formed) of macrophages, mature in tissues to macrophages
Where are granulocytes, monocytes and lymphocytes derived from?
HSCs give rise to myeloid and lymphoid stem cells -
Myeloid stem cells: Granulocytes and monocytes
Lymphoid stem cells: Lymphocytes
Which growth factors control the synthesis of granulocytes and macrophages?
Granulocyte-colony stimulating factor (G-CSF), Macrophage colony stimulating factor (M-CSF) and Granulocyte-macrophage colony-stimulating factor (GM-CSF)
Functions of Neutrophil granulocytes?
Chemotaxis, phagocytosis, killing of phagocytosed bacteria
Functions of monocytes and macrophages?
Chemotaxis, phagocytosis, killing of some micro-organisms, antigen presentation
Functions of eosinophil granulocytes?
Neutrophil functions, main defence against parasitic infections, regulating some immediate-type hypersensitivity reactions
Functions of basophil granulocytes
Neutrophil functions, mediation of immediate-type hypersensitivity reactions, modulation of inflammatory responses by releasing heparin (anti-coagulant) and proteases
Lymphocytes give what type of immunity?
Humoral and cellular immunity
What is the maturation of a granulocyte called, and what is the process?
Granulopoiesis - myoblast, promyelocyte, myelocyte, band forms, neutrophil
Cell division stops at band forms
Maturation of granulocytes is characterised by a reduction in cell size together with the development of granules that contain agents essential for cell function
Features of the neutrophil and how they function?
Segmented nucleus
Full of cytoplasmic granules
Spend 7 - 10 hours in circulation, then migrates towards tissues via chemotaxis (cytokines released from the tissue attracts neutrophils)
Adheres to vessels in infected area (margination) and migrates to tissue
Engulf, kill and digest microorganisms (phagocytosis)
Release inflammatory mediators
How do neutrophils phagocytise micro-organisms?
Release their (the neutrophil’s) toxic intracellular contents via 2 methods
What are the 2 methods for the neutrophil to release toxic contents?
- Superoxide dependent - ‘respiratory burst’ where the neutrophil releases a reactive oxygen species, which is a substrate for myeloperoxidase (MPO) leading to toxic substance production
- Oxygen dependent - antimicrobial agents are released e.g. defensins, gelatinases
Features of the eosinophil and how they function?
Spend less time in circulation
Defends against parasitic infections
Features of the basophil and how they function?
Granules contain stores of histamine (vasodilator - promotes blood flow) and heparin (prevents blood from clotting too quickly), as well as proteolytic enzymes
Appears in inflammatory responses
Features of monoctes (/macrophages) and how they function?
Spend several days in circulation
Migrate to tissues where they develop into macrophages with phagocytic properties
Phagocytosis of micro-organisms and cells that are coated with antibody and complement
Phagocytosis of bacteria and fungi not coated with antibodies
Antigen presentation to other immune cells
The lymphoid stem cell gives rise to which lymphocytes?
B cells, T cells and Natural Killer (NK) cells
Where do lymphocytes travel?
Circulate back in the bloodstream after circulating in the lymph nodes and other tissues
Function of B lymphocytes?
Mature into plasma cells that produce antibodies
The 4 roles of antibodies?
Precipitation - assist phagocytosis (bring things out of solution)
Agglutination - clumping together cells
Opsonisation - coating in antibody (antibody binds to epitope on pathogen and marks it for ingestion and destruction by phagocyte)
Neutralisation - prevent attachment of microorganisms to tissues
Where are B cells found in comparison to where plasma cells are found?
B cells - blood and tissues
Plasma cells - only in tissues
Role of the T cell?
Cell mediated immunity
Role of the NK cell?
Part of the innate response system, they can identify and attack tumour or virus infected cells
What are the 2 main types of abnormalities that can occur in white cells?
Numerical (i.e too many or too few white cell count)
Morphological (i.e shape/structure)
What are the names/types of numerical abnormalities in white cells?
Leucocytosis – too many white cells
neutrophilia
lymphocytosis
monocytosis
eosinophilia
basophilia
Leucopenia – reduction in total number of white cells
neutropenia: reduction in neutrophil count
lymphopenia: reduction in lymphocyte count
Reasons for neutrophilia (too many neutrophils)?
Infection (particularly bacterial infection), inflammation, infarction (local tissue death from obstruction of blood supply), chronic myeloid leukaemia
Pregnancy - can also result in toxic granulation (heavy granules formed)
Exercise - neutrophils attached to endothelial cells are pushed into the bloodstream
Toxic changes e.g. due to an infection can result in a left shift (increase in the number of neutrophil precursors)
Reasons for neutropenia (too few neutrophils)?
Chemotherapy and radiotherapy
Autoimmune disorders, severe bacterial infections, certain viral infections and drugs e.g. some antipsychotics
Physiological basis - i.e more common in African / Afro-Caribbean
What happens to patients with very low neutrophil counts (< 0.5 × 109/l)?
High risk of serious infection and the need urgent treatment with intravenous antibiotics
What is the name of a morphological abnormality a neutrophil could have?
Neutrophil hypersegmentation - increase in the average number of neutrophil lobes or segments (normal neutrophil should have between 3 and 5 segments)
Reasons for Neutrophil hypersegmentation?
Usually results from a lack of vitamin B12 or folic acid
Reasons for Lymphocytosis (too many lymphocytes)?
Response to viral infection (transient)
Leukaemia (persistent)
Whooping cough (in children)
Definition of lymphomenia and what type of cells it mainly consists of?
Lymphocytes are mainly CD4+ T cells, and lymphomenia is defined as a total lymphocyte count < 1 × 10^9 /l
Usually due to low neutrophil count
Reasons for Lymphopenia (too few lymphocytes)?
HIV infection Chemotherapy Radiotherapy Cortico-steroids Severe infection
Reasons for Monocytosis (too many monocytes)?
Infection (particularly chronic bacterial infection) or chronic inflammation
Some types of leukemia
Reasons for Eosinophilia (too many eosinophils)?
Usually due to allergy or parasitic infection i.e asthma, eczema, drugs
Leukemia
Reasons for Basophilia (too many basophils)?
Very uncommon, usually due to leukemia (or a related condition)
Summary: Transient leucocytosis is frequently associated with?
Infection
Bacterial: neutrophilia / monocytosis
Viral: lymphocytosis
Parasitic: eosinophilia
Summary: Persistent leucocytosis may be caused by?
Leukemia
Chronic lymphocytic leukaemia, CLL (lymphocytosis)
Chronic myeloid leukaemia, CML
(neutrophilia, basophilia, eosinophilia)
How to identify the type of white cell from an image?
Neutrophil, 3-5 segments
Eosinophil, has a slight orange-brown colour
Basophil - purple, kinda dotty
Monocyte - crescent
Lymphocyte - round or rectangular-ish (many shapes)
