THE DEVELOPMENT OF B-LYMPHOCYTES

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THE DEVELOPMENT OF B-LYMPHOCYTES
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STAGES IN LIFE CYCLE OF B-LYMPHOCYTES

• Stage 1
• Maturation in bone marrow with development of
  functional receptors
• Stage 2
• Testing for and elimination of self-reactive
  receptors
• Stage 3
• Mature naïve cells move to secondary lymphoid
  tissues
• Stage 4
• Antigen contact with differentiation into plasma
  cells and memory cells

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B-CELL DEVELOPMENT IN BONE MARROW

• Stages are defined by rearrangement and
  expression of IG genes
• Early Pro-B cells
• Earliest cells in B-cell lineage
• Rearrangement of variable domain of heavy chains
• D to J
• Late Pro-B cell
• Rearrangement of variable domain of heavy chains
• V to DJ

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B-CELL DEVELOPMENT IN BONE MARROW

• Large Pre-B cell
• M expressed on cell surface along with surrogate
  light chains and signal transduction molecules
• Pre-B cell receptor
• Small Pre-B cell
• Pre-B cell receptor not present
• Most M chains inside cell
• Light chain rearrangement begins

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B-CELL DEVELOPMENT IN BONE MARROW

• Immature B-cell
• Heavy and light chains assembled and transported
  to surface as IgM receptor complex
• Randomness of gene rearrangements leads to
  self-reactive B-cells
• Mature B-cell
• IgD expressed on cell surface
• Called naïve B-cells

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Figure 4-4
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B-CELL DEVELOPMENT IN BONE MARROW

• Development depends on non-lymphoid stromal cells
• Function of stromal cells
• Specific contact through cell adhesion molecules
  (CAMs)
• VCAM-1 to VLA-4 on early pro-B cells
• Produce growth factors for bound B-cells
• Stem cell factor (SCF)
• Interleukin-7 (IL-7)
• Growth factors
• Stem cell factor stimulates (G/P) of Early pro-B
  cells
• Interleukin-7 stimulates (G/P) of Late pro-B and
  L/S pre-B cells

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GENE REARRANGEMENTS AND B-CELL SURVIVAL

• Gene rearrangement process is imprecise and
  classified as
• Unproductive
• Not translated into IG chain
• B-cell dies
• Productive
• Translated into IG chain
• Development proceeds
• Immunoglobulin loci
• Each B-cell has 2 copies on homologous
  chromosomes
• Rearrangements made on both

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PROTEINS INVOLVED IN REARRANGEMENT AND EXPRESSION
OF IG GENES

• Several categories of specialized proteins are
  required
• Lymphoid specific recombination
• RAG-1 and RAG-2
• N-nucleotide addition
• TdT
• Surrogate light chains
• Lambda5 and VpreB
• Signal transduction
• IG-alpha, IG-beta, CD45 and Btk
• Transcription factors
• EBF and Oct-2

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SIGNAL TRANSDUCTION AND BRUTONS TYROSINE KINASE
(BTK)

• Brutons tyrosine kinase (Btk)
• Encoded by gene on X chromosome
• Essential for B cell maturation
• Mutation in gene
• B cells maturation stops at pre-B cell stage
• Results in immunodeficiency called
• Brutons X-linked agammaglobulinemia
• Immunodeficiency results in recurrent
  sinopulmonary infections with
• Streptococcus pneumoniae
• Haemophilus influenzae

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POPULATIONS (SUBSETS) OF B CELLS

• B-1 cells (minor subset)
• Develop early in embryonic life with unknown
  origin
• Express CD5 (CD5 B cells)
• Self-renewing
• Primary location is body cavities (pleural /
  peritoneal)
• Produce polyspecific antibodies
• B-2 cells (major subset)
• Develop after birth
• Do not express CD5 glycoprotein
• Replaced from bone marrow
• Primary location is lymphoid organs
• Produce highly specific antibodies

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NEGATIVE SELECTION AND FURTHER DEVELOPMENT OF B
CELLS

• Self reactive immature B cells are either
• Eliminated or inactivated
• IgM receptor may react with
• Cell surface or soluble self antigens
• Reactions with cell surface antigens
• Induced to commit suicide by apotosis
• Clonal deletion
• Reactions with soluble antigens
• Rendered unresponsive (anergic) to antigen
• Maturation continues with reduced surface IgM

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SELECTION AND FURTHER DEVELOPMENT OF B CELLS

• B cells leave bone marrow and circulate between
  blood and secondary lymphoid tissues
• Secondary lymphoid tissue contains primary
  lymphoid follicles
• Primary lymphoid follicle
• Area where B cells congregate in association with
  specialized stromal cells (follicular dendritic
  cells)
• Passage through primary lymphoid follicle and
  contact with follicular dendritic cells (FDC)
  necessary for survival
• Few days with no passage
• 3 to 8 weeks with passage

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CIRCULATION OF B CELLS THROUGH SECONDARY LYMPHOID
TISSUES (LYMPH NODES)

• Chemokines attract B cells to leave blood and
  enter cortex of lymph node via high endothelial
  venule (HEV)
• Chemokines attract B cells to lymph node and
  primary lymphoid follicle
• No encounter with antigen
• B cells leave node via efferent lymphatic vessel
• Anergic B cells detained in T cell area
• Induced to commit suicide by apoptosis

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B CELL ENCOUNTER WITH ANTIGEN IN SECONDARY
LYMPHOID TISSUES

• Encounter with antigen takes place in T cell area
  of lymph node cortex
• Antigen reached lymph node from infected tissue
  via afferent lymphatic vessel
• B cell is activated by CD4 T-cell in T-cell area
• Activated B cells
• Migrate to medulla area and differentiate into
  plasma cells
• Migrate to primary follicle to form germinal
  center
• Migrate to medulla or bone marrow and complete
  differentiation into plasma cells
• Develop into memory B cells

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B-LYMPHOCYTE TUMORS

• Caused by mutations in genes that regulate cell
  growth
• Genes regulating cell growth
• Proto-oncogenes
• Promotes cell growth
• Tumor suppressor genes
• Inhibits cells growth
• Mutations in growth regulating genes
• Transformation into oncogenes (cancer causing
  genes)

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B LYMPHOCYTE TUMORS

• Represents uncontrolled growth of single
  transformed B cell
• Associated with all stages of development
• Tumors retain characteristics of cell type and
  location
• Hodgkins Lymphoma
• Germinal center B cell in lymphoid tissue
• Multiple myeloma
• Plasma cell in bone marrow
• Waldenstroms macroglobulinemia
• IgM secreting B lymphocyte in lymphoid tissue
• Burkitts lymphoma
• Resembles germinal center B cell in lymphoid
  tissue

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Figure 4-19
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HODGKINS DISEASE (LYMPHOMA)

• Hodgkins disease is a type of lymphoma
• Two types of lymphoma
• Hodgkins disease
• Non-Hodgkins lymphoma (NHL)
• Two main types of Hodgkins disease
• Classical (95)
• Nodular lymphocyte predominance (5)
• Disease most often starts in lymph nodes of upper
  body
• Chest, neck or under the arms

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HODGKINS DISEASE (LYMPHOMA)

• Cause is not known but there are risk factors
• Epstein-Barr Virus (EBV) infection
• Geography
• United States, Canada, northern Europe
• Family history
• Identical twin (very high)
• Approximately 8,000 new cases each year in US
• Cancer cells of HD are unique
• Reed-Sternberg cells

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WALDENSTROMS MACROGLOBULINEMIA

• Indolent, non-Hodgkins lymphoma (NHL)
• Classified as
• Monoclonal gammopathy
• Cancer cells
• Features of B-cells and plasma cells
• Lymphoplasmacytoid
• Located primarily in bone marrow
• Produce large amounts of monoclonal protein
  (antibody)
• IgM
• Approximately 1,500 new cases each year in US

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MULTIPLE MYELOMA

• Aggressive, non-Hodgkin lymphoma
• Classified as
• Monoclonal gammopathy
• Cancer cells
• Abnormal plasma cells (myeloma cells)
• Located primarily in bone marrow
• Produce monoclonal proteins (antibody)
• IgG, IgA, free kappa or lambda light chains
• Approximately 20,000 cases in US for 2008

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BURKITTS LYMPHOMA

• B cell tumor with 2 forms
• Endemic (African)
• Facial tumors
• Strongly associated with EBV infection
• Nonendemic (Sporadic)
• Abdominal tumors
• Characteristic translocation
• MYC proto-oncogene on chromosome 8 to IG genes
• Chromosome 14 (90)
• Chromosomes 2 and 22 (10)
• MYC protein
• Normally regulates cell division
• Control is lost following translocation to IG gene

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CASE STUDY 21 YEAR OLD MALE

• 21 year old WM presents with
• Fever (102 F)
• Sore throat
• Moderate malaise, myalgia and fatigue
• Difficulty in swallowing
• H and P
• Healthy and sexually active
• Bilateral anterior and posterior cervical
  lymphadenopathy
• Pharyngeal inflammation
• Mild splenomegaly and no jaundice

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CASE STUDY 21 YEAR OLD MALE

• Admitted to MC and administered
• Penicillin G
• Prednisone
• Valacyclovir
• Laboratory tests
• CBC with diff
• Liver function tests
• Monospot test (Heterophile antibody)
• Erythrocyte sedimentation rate (ESR)
• Group A streptococcus antigen

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CASE STUDY 21 YEAR OLD MALE

• CBC with diff
• WBC 12.5
  4.8-10.8 K/uL
• RBC 4.0
  3.93-5.22 M/uL
• Platelets 250
  150-450 K/uL
• Hemoglobin 14.0
  11.2-15.7 g/dL
• Hematocrit 40
  34.1-44.9
• Neutrophils 45
  40-74
• Lymphocytes 55
  15-47
• Atypical lymphocytes 18
  
• Monocytes 12
  0-12

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REACTIVE (ATYPICAL) LYMPHOCYTES

• Larger in size
• Up to 30 um in diameter
• More cytoplasm
• Less dense nuclear chromatin
• Irregular shaped nucleus
• Nucleous may be present
• Periphery of cell show scalloped edge

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CASE STUDY 21 YEAR OLD MALE

• Liver function tests
• ALT 130
  19-55 U/L
• AST 112
  15-37 U/L
• Alk phos 150
  50-136 U/L
• ESR 40
  0-30 mm/hr
• GAS antigen Negative
  Negative
• Monospot test Positive
  Negative

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CASE STUDY 21 YEAR OLD MALE

• Patient discharged after 36 hours
• Treatment
• NSAID
• Recommendations
• Avoid sports
• Avoid alcohol

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CASE STUDY 18 YEAR OLD FEMALE

• 18 year old HF presents with
• Fever (101 F)
• Sore throat
• Moderate malaise, myalgia and fatigue
• Difficulty in swallowing
• H and P
• Healthy and sexually active
• Bilateral anterior and posterior cervical
  lymphadenopathy
• Pharyngeal inflammation
• Mild splenomegaly and no jaundice

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CASE STUDY 18 YEAR OLD FEMALE

• Admitted to MC and administered
• Penicillin G
• Prednisone
• Valacyclovir
• Laboratory tests
• CBC with diff
• Liver function tests
• Monospot test (Heterophile antibody)
• Erythrocyte sedimentation rate (ESR)
• Group A streptococcus antigen

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CASE STUDY 18 YEAR OLD FEMALE

• CBC with diff
• WBC 13.5
  4.8-10.8 K/uL
• RBC 4.2
  3.93-5.22 M/uL
• Platelets 260
  150-450 K/uL
• Hemoglobin 14.5
  11.2-15.7 g/dL
• Hematocrit 42
  34.1-44.9
• Neutrophils 46
  40-74
• Lymphocytes 56
  15-47
• Atypical lymphocytes 20
  
• Monocytes 12
  0-12

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CASE STUDY 18 YEAR OLD FEMALE

• Liver function tests
• ALT 136
  19-55 U/L
• AST 115
  15-37 U/L
• Alk phos 156
  50-136 U/L
• ESR 42
  0-30 mm/hr
• GAS antigen Negative
  Negative
• Monospot test Negative
  Negative

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CASE STUDY 18 YEAR OLD FEMALE

• Epstein-Barr Virus serology (IFA)
• Viral capsid antigen (VCA) IgM 1320
  lt 120
• Viral capsid antigen (VCA) IgG 140
  lt 110
  
• Early antigen (D R) IgG
  120 lt 110
• Nuclear antigen (NA) IgM
  180 lt 110
• Nuclear antigen (NA) IgG lt
  110 lt 110

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CASE STUDY 18 YEAR OLD FEMALE

• Patient discharged after 24 hours
• Treatment
• NSAID
• Recommendations
• Avoid sports
• Avoid alcohol

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CASE STUDY 24 YEAR OLD FEMALE

• 24 year old WF presents with
• Fever (101 F)
• Moderate malaise and fatigue
• Myalgia and bone pain
• Shortness of breath
• H and P
• No significant history
• Generalized lymphadenopathy
• Pallor
• Mild splenomegaly and no jaundice

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CASE STUDY 24 YEAR OLD FEMALE

• Admitted to MC with diagnosis of
• Pneumonia and anemia
• Laboratory tests
• CBC with diff
• Monospot test (Heterophile antibody)
• Pregnancy test
• Influenza A and B antigens

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CASE STUDY 24 YEAR OLD FEMALE

• CBC with diff
• WBC 44.4
  4.8-10.8 K/uL
• RBC 1.0
  3.93-5.22 M/uL
• Platelets 8
  150-450 K/uL
• Hemoglobin 3.6
  11.2-15.7 g/dL
• Hematocrit 11.3
  34.1-44.9
• Neutrophils 6
  40-74
• Lymphocytes 10
  15-47
• Atypical lymphocytes 0
  
• Monocytes 20
  0-12
• Blasts 55
  

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CASE STUDY 24 YEAR OLD FEMALE

• Pregnancy test Negative
  Negative
• Influenza antigens Negative
  Negative
• Monospot test Positive
  Negative
• Peripheral blood smear
• RBCs showing anisopoikocytosis. Leukocytes show
  predominance of blasts many with cytoplasmic
  granules. Mature granulocytes show dysplastic
  features. Monocytes are atypical.

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CASE STUDY 20 YEAR OLD FEMALE

• 20 year old WF presents to ED c/o
• Chest pain
• POCT
• Troponin 23.21 lt 0.7
  ng/mL
• CK MB 44.8 lt 3.6
  ng/mL
• CK, Total 611 21 215
  U/L
• Admitted to MC with diagnosis of
• STEMI (ST segment elevation myocardial
  infarction)
• Transported to Cardiac Catheterization Laboratory

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CASE STUDY 20 YEAR OLD FEMALE

• History and Physical
• Leg and hip pain 1 day prior
• Diagnosis of IM 1 month prior
• CBC with DIFF
• WBC 8.6
  4.8-10.8 K/uL
• RBC 3.86
  4.00-5.40 M/uL
• Platelets 179
  145-400 K/uL
• Neutrophils 66 40-74
  
• Lymphocytes 24 15-47
  
• Monocytes 10 0-12
  

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CASE STUDY 20 YEAR OLD FEMALE

• Cardiac catheterization
• Blockage of left anterior descending artery

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CASE STUDY 20 YEAR OLD FEMALE

• Lipid profile
• Cholesterol 134
  lt 200 mg/dL
• HDL 42
  gt 40 mg/dL
• LDL 74
  lt 130 mg/dL
• Triglycerides 90
  lt 200 mg/dL
• Homocysteine 5.6
  lt 10.4 umol/L
• Lipoprotein(a) 15
  lt 75 mg/dL
• Cardiolipin antibody Positive
  Negative

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CASE STUDY 20 YEAR OLD FEMALE

• Mononucleosis test
• Positive (strong)
• EBV early antigen, IgG
• Negative
• CBC with DIFF
• Normal

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