8.1 Myeloblast; promyelocyte; myelocyte; metamyelocyte; band form; effector cell.
8.2 A leukaemoid reaction is a polyclonal reactive condition and is associated with a white cell count of 50 ´ 109/l or higher in which mature white cells and their precursors are found within the peripheral blood.
8.3 Primary granules are synthesized at the promyelocyte stage of maturation. Secondary and tertiary granules are synthesized at the myelocyte and metamyelocyte stages of development in response to CEBPe.
8.4 Neutropenia describes a neutrophil count two or more standard deviations below the mean for the patient’s population – i.e. the patient’s neutrophil count is below its appropriate reference range. If the neutrophil count drops below 0.5 ´ 109/L, the patient is at significant risk from developing life-threatening bacterial and fungal infections.
8.5 During infection, chemotaxins are produced from the site of infection producing a concentration gradient of chemical mediators. The highest concentration is at the source of infection, with the concentration decreasing proportionally to the distance of the infection. Following chemotactic stimulation, neutrophils will adhere to the vascular endothelium near the site of injury in a process called margination. Once inside the tissue space, neutrophils follow the chemotactic gradient to the site of infection using cytoskeletal rearrangement.
8.6 Eosinophil secondary granules contain high concentrations of bactericidal arginine-rich basic proteins. These arginine-rich proteins include:
major basic protein—disrupts the lipid bilayer of parasites and target cells.
eosinophil peroxidase—is bactericidal and can form reactive singlet oxygen and hypobromous acid in the presence of H2O2 and bromide.
eosinophil cationic protein—bactericidal and helminthotoxic.
eosinophil-derived neurotoxin/eosinophil protein X (EDN/EPX)—possesses important bactericidal and helminthotoxic activity and also possesses RNase activity.
Basophils are granulocytes which play an important role in allergy and inflammation. Basophil granules contain histamine which is released in the presence of allergens and plays an important role in vascular permeability.
Monoblasts; promonoblast; promonocyte; monocyte.
Monocytes enter the tissues and mature into macrophages. Macrophages will then undergo additional series of DNA synthesis and mitosis forming colonies of macrophages. Mitosis ceases and endomitosis occurs resulting in the formation of giant cells.
Pre-B cells shows evidence of IgM heavy chain synthesis within the cytoplasm. As pre-B cells mature to an immature B-cell, light chains are synthesized and combine with the heavy chains forming a complete surface bound B-cell receptor. Mature B-cells express both IgM and IgD on their cell surface.
Somatic hypermutation is the process through which antibody affinity is increased. Following interaction with antigen, B-cells undergo proliferation and somatic hypermutation. Somatic hypermutation involves base-pair substitutions within the hypervariable region of the immunoglobulin in order to improve the ‘fit’ between antigen and antibody.
Cytotoxic T-cells interact with HLA class I presented viral peptides via CD8 inducing degranulation and the release of perforins and granzymes. Perforins and granzymes induce osmotic lysis and apoptosis of infected cells.
Patients with infectious mononucleosis (IM) tend to have a raised white cell count due to an absolute lymphocytosis. Examination of the blood film demonstrates a lymphocytosis with a reactive picture. The lymphocyte cytoplasm can be deeply basophilic and the membrane of the reactive T-cells scallops around the membrane of neighbouring cells. Patients are likely to demonstrate a reaction with ox cells but not guinea pig cells in the Paul–Bunnell test and the latex agglutination test is usually positive.