Biology 201 Fundamentals of Biology II

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Biology 201Fundamentals of Biology II

• Rob Mustard
• Adjunct Faculty

PALOMAR COLLEGE
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Leukocytes Immune Response

• Blood cells are one of the fluid Connective
  Tissues
• Red blood cells (erythrocytes)
• Mammalian RBCs lack nuclei and mitochondria
• 7 ?m diameter
• White blood cells(leukocytes)
• Giemsa stain to differentiate WBCs

6-7 million erythrocytes / ml3 7,000 leukocytes /
ml3
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Immune Response Modes

• Innate Immunity
• Rapid (and general) response to a broad range of
  microbial invasion
• Acquired (Adaptive) Immunity
• Secondary (and highly-specific) response to
  previously-encountered pathogens
• Vertebrates have both forms of immune-response
  mechanisms

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Innate Immunity

• External defenses include
• Skin impenetrable to most viruses bacteria
• Mucous viscous fluid that traps microbes
• Cellular secretions sebaceous (oil) sweat
  glands reduce skins pH to 3-5 lysozyme digests
  Gram cell walls
• Internal defenses begin after bacteria invade,
  typically through a break in skin or other
  epidermal layer

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Inflammatory Response

• Tissue damage from physical injury leads to
  cascade of chemical signals
• Histamine, stored in mast cells in connective
  tissue
• Nearby capillaries become dilated and leaky,
  allowing passage of macrophages and increased
  blood flow
• Increased local blood supply leads to redness,
  heat and swelling (inflammation)
• Macrophages move out into damaged tissues, in
  interstitial spaces between cells
• Nonspecific Inflammatory Response

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Leukocytes Involved in Innate Immunity
Phagocytes

• Neutrophils
• 60-70 of all leukocytes, live only a few days
• Big 12-15 ?m (2x erythrocytes)
• Nucleus has 2-5 lobes (polymorphic)
• Monocytes
• 5 of all leukocytes
• Biggest 20 ?m
• Lighter, frothy horseshoe-shaped nucleus

Neutrophils are granular
Monocytes are agranular
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Leukocytes Involved in Innate Immunity
Phagocytes

• Eosinophils
• Rare in blood smears (2-4)
• Big 12-15 ?m (same size as Neutrophils)
• Nucleus has 2 lobes
• Dendritic Cells
• Patrol interstitial spaces of skin mucosal
  membranes
• Phagocytize invaders, process present antigen
  material (APCs)
• Activate acquired immune system

Eosinophils are granular
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Leukocytes Involved in Innate Immunity
Hypersensitivity

• Basophils
• Rarest of the leukocytes (lt0.5)
• 10-12 ?m diameter
• Respond to allergic reactions (e.g., bee wasp
  stings, pollen)
• Very granular nucleus often obscured
• Live for about 2 weeks

Basophils are very granular
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Leukocytes Involved in Innate Immunity
Cytotoxicity

• Natural Killer Cells
• A specialized lymphocyte
• Attack virus-infected cells
• Attack cancer cells (tumors)
• NK cells recognize infected/defective cells via
  surface features
• Bind to target cells, release chemicals
  (perforins) that lead to apoptosis

An NK cell (N) attached to a "target" cell "T".
The NK cell will kill the now helpless target
cell quickly, by the injection of deadly perforin.
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Leukocytes Involved in Acquired Immunity

• Lymphocytes
• Very common in blood 20-40 of WBCs
• Slightly larger than RBCs (10 ?m)
• Dark-staining, circular nucleus
• Agranular cytoplasm is transparent

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Lymphocyte Specialization

• Vertebrate lymphocytes take on specialized roles
• Circulate through blood lymph, concentrated in
  spleen lymph nodes
• B T cells bear 100K antigen receptors (all the
  same)

Antigen- binding sites
IgM Receptors
V
V
Variable regions
V
Light chain
V
V
V
C
C
C
C
C
C
Constant regions
b chain
? chain
Heavy chains
T cell
B cell
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Acquired Immunity Responses

• Humoral Response
• Dendritic cell (APC) engulfs pathogen, presents
  antibody via cell-surface protein (MHC class II)
• Helper T cell binds to presented antigen
• APC releases cytokines to stimulate production of
  more activated T cells
• Activated B cells secrete antibodies, which
  immobilize pathogens, marking them for
  destruction by macrophages
• Cellular Immune Response
• A cell other than a leukocyte takes up and kills
  a microbe, presents antigen on surface (MHC class
  I)
• Cytotoxic (activated) T cell binds to presented
  antigen, releases perforins, lyses infected cell

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• Questions??

PALOMAR COLLEGE