lecture 10

Question 1

What are the adult reference ranges for blood cells?

Answer 1

• white cells (x10^3/µL) = 4.8-10.8
• granulocytes (%) = 40-70
• neutrophils (x10^3/µL) = 1.4-6.5
• lymphocytes (x10^3/µL) = 1.2-3.4
• monocytes (x10^3/µL) = 0.1-0.6
• eosinophils (x10^3/µL) = 0-0.5
• basophils (x10^3/µL) = 0-0.02
• red cells (x10^3/µL) = 4.3-5, men; 3.5-5.0, women
• platelets (x10^3/µL) = 150-450

Question 2

How are reference ranges used?

Answer 2

• if someone lies outside the range it can indicate disease

Question 3

How do blood cells develop?

Answer 3

• from HSCs through well defined paths of differentiation, of which a number of the important transcription factors/chemokines are known

Question 4

Where is the ‘haematopoietic stem cell niche?

Answer 4

• in the bone marrow

- endosteal part of bone

Question 5

What cell types are found in the niche?

Answer 5

• endothelial cells
• nerve cells: can direct stem cell differentiation
• osteoblasts: may have a role in signalling
• stromal cells

Question 6

What organs are important for the development and maturation of WBCs?

Answer 6

• bone marrow: where they arise
• lymph nodes
• thymus: almost exclusively T cells
• spleen

Question 7

What are some of the major white blood cell types?

Answer 7

• B lymphocyte: antibody secretion after detection of antigen and differentiation into plasma cells
• CD4+ helper T lymphocyte: after presentation of antigen they release cytokines which stimulate activation of macrophages, inflammation and B lymphocytes
• CD8+ cytotoxic T lymphocyte: kill infected body cells

Question 8

What are all the names for neutrophils?

Answer 8

• neutrophil
• polymorphonuclear leukocyte, PMN, PML
• “Leukocyte”
• granulocyte, neutrophilic granulocyte
• polymorph

Question 9

What does a neutrophil generally look like?

Answer 9

• lobular nucleus

Question 10

What are the functions of a neutrophil?

Answer 10

• margination
• rolling
• adhesgion
• transmigration (diapedesis)
• chemotaxis
• phagocytosis: recognition, engulfment, killing (digestion)
• equilibrium with splenic pool

Question 11

What is leukopenia?

Answer 11

• the number of circulating white cells may be markedly decreased in a variety of disorders
• an abnormally low white cell count (leukopenia) usually results from reduced numbers of neutrophils

Question 12

What is neutropenia?

Answer 12

• a reduction in the number of neutrophils in the blood, occurs in a wide variety of circumstances

Question 13

What is agranulocytosis?

Answer 13

• a clinically significant reduction in neutrophils – susceptibility to bacterial and fungal infections

Question 14

What are reasons for inadequate production of neutrophils?

Answer 14

• stem cell suppression e.g. aplastic anaemias
• drugs especially chemo, many antibiotics
• inherited defects in specific genes impairing granulocytic differentiation - Kostmann Syndrome

Question 15

What are reasons for increased destruction of neutrophils?

Answer 15

• immune mediated
  – idiopathic, or consequence of immune disorder, e.g. SLE (system lupus erythematosus )
  – after “sensitisation” by drugs - antibiotics
• splenic sequestration, spleen-blockage-enlargement - can be fatal in children
• increased peripheral demand, as in overwhelming infections, especially fungal

Question 16

What is leukocytosis?

Answer 16

Increase in the number of white cells in the blood.

Reaction to a variety of inflammatory states.

Question 17

What is the pathogenesis of leukocytosis influenced by?

Answer 17

• size of the myeloid and lymphoid precursor and storage cell pools in the bone marrow, thymus, circulation and peripheral tissues
• rate of release of cells from the storage pools into the circulation
• the proportion of cells that are adherent to blood vessel walls at any time (the marginal pool)
• the rate of extravasation of cells from the blood into tissues

Question 18

What is leukocytosis often accompanied by in sepsis or severe inflammatory disorders?

Answer 18

• morphologic changes in the neutrophils

- e.g. toxic granulations, Döhle bodies, and cytoplasmic vacuoles

Question 19

What is lymphadenitis?

Answer 19

Acute nonspecific lymphadenitis - usually self limiting

• very sore lymph nodes
• caused by microbial drainage from infections of the teeth or tonsils
• acute lymphadenitis in mesenteric lymph nodes draining acute appendicitis
• systemic viral infections (particularly in children) and bacteremia often produce acute generalised lymphadenopathy

Question 20

What are lymphoid neoplasms?

Answer 20

• include a diverse group of tumours of B-cell, T-cell, and NK-cell origin
• in many instances the phenotype of the neoplastic cell closely resembles that of a particular stage of normal lymphocyte differentiation, a feature that is used in the diagnosis and classification of these disorders?

Question 21

What are myeloid neoplasms?

Answer 21

• arise from early haematopoietic progenitors
  3 categories of myeloid neoplasia:
• acute myeloid leukaemias (AML), in which immature progenitor cells accumulate in the bone marrow
• myelodysplastic syndromes, which are associated with ineffective haematopoiesis and resultant peripheral blood cytopenias
• chronic myeloproliferative leukemia (CML) - increased production of one or more terminally differentiated myeloid elements (e.g. granulocytes) usually leads to elevated peripheral blood counts

Question 22

What are the etiologic and pathogenetic factors in white cell neoplasia?

Answer 22

• nonrandom chromosomal abnormalities, most commonly translocations, are present in the majority of white cell neoplasms
• these translocations result in gene fusions generating abnormal oncogenic mRNAs and proteins
• e.g. The philadelphia chromosome t(9;22) is present in approximately 3% of children with ALL and leads to production of a BCR-ABL1 fusion protein with tyrosine kinase activity

Question 23

Why are white cells so prone to translocation disorders?

Answer 23

• because they’re dividing rapidly, increasing the statistical chance that something may happen
• also perhaps genetically predisposed to not being able to check for errors properly

Question 24

What is the molecular pathogenesis of acute leukaemia?

Answer 24

• acute leukaemia arise from complementary mutations that block differentiation at early stages of white cell development, enhance self-renewal, and increase growth and survival
• e.g. BCR-ABL, breakpoint chromosomal region - Abelson kinase fusion gene; PML-RAR-alpha, promyelocyctic leukaemia-retinoic acid receptor alpha fusion; MLL, mixed-lineage leukaemia gene
• BCR-ABL leads to increased growth of progenitor cells, tyrosine kinase mutation
• PML-RAR-alpha blocks transcription factor mutations that lead to differentiation

MLL: fusion with FPG (abnormal function), or repeat of part of MLL gene producing a duplicate domain

Question 25

What is the molecular pathogenesis of acute leukaemia?

Answer 25

chronic immune stimulation

• several environmental agents that cause localised chronic immune stimulation predispose to lymphoid neoplasia, which almost always arises within the inflamed tissue
• H. pylori infection and gastric B-cell lymphomas
• Gluten-sensitive enteropathy and intestinal T-cell lymphomas

Iatrogenic factors

• radiation therapy and certain forms of chemotherapy used treat cancer increase the risk of subsequent myeloid and lymphoid neoplasms
• stems from the mutagenic effects of ionising radiation and chemotherapeutic drugs on hematolymphoid progenitor cells

Smoking
- the incidence of AML is increased 1.3- to 2-fold in smokers, due to exposure to carcinogens, such as benzene, in tobacco smoke

Question 26

What are the three major lymphotropic viruses?

Answer 26

• human t-cell leukaemia virus-1 (HTLV-1)
• epstein-barr virus (EBV)
• kaposi sarcoma herpesvirus/human herpesvirus-8 (KSHV/HHV-8)

Question 27

From which cells do lymphoid neoplasms normally arise?

Answer 27

• the vast majority (85% - 90%) of lymphoid neoplasms are of B-cell origin, with most of the remainder being T-cell tumours

Question 28

What is leukaemia?

Answer 28

• involve bone marrow and (usually, but not always) the peripheral blood

Question 29

What are lymphomas?

Answer 29

arise as discrete tissue ‘tumours’ - e.g. in lymph nodes

Question 30

What are the common clinical features of ALL?

Answer 30

• abrupt stormy onset within days to a few weeks of the first symptoms
• symptoms related to depression of marrow function, including fatigue due to anaemia; fever, reflecting infections secondary to neutropenia; and bleeding due to thrombocytopenia
• mass effects caused by neoplastic infiltration (which are more common ALL), including bone pain resulting from marrow expansion; generalised lymphadenopathy, splenomegaly, a hepatomegaly; testicular enlargement; and in T-ALL, complications related to compression of large vessels and airways in the mediastinum
• (not common)central nervous system manifestations such as headache, vomiting, and nerve palsies resulting from meningeal spread, all of which are also more common in ALL

Question 31

What is the prognosis for someone with ALL?

Answer 31

• with aggressive chemotherapy about 95% of children with ALL obtain a complete remission, and 75% to 85% are cured
• however ALL remains the leading cause of cancer deaths in children, and only 35% to 40% of adults are cured

Question 32

What is ALL?

Answer 32

Acute lymphoblastic leukaemia/lymphomas

• composed of immature B (pre-B) or T (pre-T) cells, which are referred to as lymphoblasts
• about 85% are B-ALLs, which typically manifest as childhood acute “leukaemias”
• the less common T-ALLs tend to present in adolescent males and thymic “lymphomas”

Question 33

How do we diagnose ALL?

Answer 33

• blood smear (morphology) - accumulation of ‘blasts

- expression of particular markers/known receptors - e.g. intracellular TdT, CDs (22, 19, 10)

Question 34

What are the molecular features of ALL?

Answer 34

• approximately 90% of ALLs have numerical or structural chromosomal changes/mutations
• with respect to gene mutations: single mutations are not sufficient to produce ‘ALL’
• studies of identical twins with concordant B-ALL: same mutation but different ‘evolution’ over time ie. further mutations required
• many of the chromosomal aberrations seen in ALL d ysregulate the expression and function of transcription factors that are required for normal B- and T-cell development
• T-ALLs - NOTCH1 TF
• B-ALLs - PAX5, E2A, TFs

Question 35

How can you detect the difference between AML and ALL via blood smear?

Answer 35

AML

• more cytoplasm in blast cells
• CD34, CD64, CD33, CD15

ALL

• most taken up by nucleus
• intracellular TdT, CDs (22, 19, 10)

Question 36

What is multiple myeloma?

Answer 36

• causes 1% of all cancer deaths in Western countries
• Its incidence is higher in men and people of African descent
• It is chiefly a disease of the elderly, with a peak age of incidence 65 to 70 years
• plasma cell neoplasm characterised by multifocal involvement of the skeleton
• less common manifests in lymph nodes and/or skin
• normal marrow cells are largely replaced by plasma cells, including forms with multiple nuclei, prominent nucleoli, and cytoplasmic droplets containing Ig

Question 37

What is the biochemical diagnosis of MM?

Answer 37

• in 99% of patients, laboratory analyses reveal increased levels of Igs in the blood and/or light chains (Bence Jones proteins) in the urine
• the most common monoclonal Ig (“M protein”) is IgG (~55% of patients), followed by IgA (~25% of cases)
• myelomas expressing IgM, IgD, or IgE occur but are rare
• you get a really thick band as opposed to a smear on gel electrophoresis

Question 38

What is the molecular and cellular pathogenesis of MM?

Answer 38

• the Ig genes in myeloma cells always show evidence of somatic hypermutation
• the cell of origin is considered to be a post-germinal centre B cell that homes to the bone marrow and has differentiated into a plasma cell
• may originate in and be maintained by stem-like cells resembling small B lymphocytes via oncogenic signals generated by the “hedgehog” pathway for self-renewal
• a key factor promoting the proliferation and survival of myeloma cells is IL-6 via autocrine and paracrine signalling from stromal cells
• factors produced by neoplastic plasma cells mediate bone destruction, the major pathologic feature of multiple myeloma
• myeloma-derived MIP1-alpha upregulates the expression of the receptor activator NF-kappaB ligand (RANKL) by bone marrow stromal cells, which in turn activates osteoclasts
• further enhancing this effect is the Wnt-pathway mediated inhibition of osteoblasts

Question 39

What is the prognosis and treatment of MM?

Answer 39

• prognosis is variable but generally poor
• median survival is 4 - 6 years, and cures have yet to be achieved
• patients with multiple bony lesions, if untreated, rarely survive for more than 6-12 months, whereas patients with “smouldering myeloma” may be asymptomatic for many years
• translocations involving cyclin D1 are associated with a good outcome, whereas deletions of 13q, deletions of 17p, and the t(4;14) all require aggressive therapies
• chemotherapy induces remission in 50% to 70% of patients

Question 40

What is Anaplastic Large-Cell Lymphoma?

Answer 40

• defined by the presence of rearrangements in the anaplastic lymphoma kinase (ALK) gene
• rearrangements break the anaplastic lymphoma kinase (ALK) locus and lead to the formation of chimeric genes encoding ALK fusion proteins, constitutively active tyrosine kinases that trigger a number of proliferation and survival signalling pathways, including the JAK/STAT pathway
• the cure rate with chemotherapy is 75% to 80%
• inhibitors of ALK are under development and offer an excellent opportunity for the development of a selective, targeted therapy
• ALK-specific antigen vaccine