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Biology 201 Fundamentals of Biology II. Rob Mustard Adjunct Faculty. PALOMAR COLLEGE. 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

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biology 201 fundamentals of biology ii

Biology 201Fundamentals of Biology II

Rob Mustard

Adjunct Faculty

PALOMAR COLLEGE

PALOMAR COLLEGE

leukocytes immune response
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

PALOMAR COLLEGE

immune response modes
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

PALOMAR COLLEGE

innate immunity
Innate Immunity

External defenses include:

Skin: impenetrable to most viruses & bacteria

Mucous: viscous fluid that traps microbes

Cellular secretions: sebaceous (oil) & sweat glands reduce skin’s 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

PALOMAR COLLEGE

inflammatory response
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

PALOMAR COLLEGE

leukocytes involved in innate immunity phagocytes
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

PALOMAR COLLEGE

leukocytes involved in innate immunity phagocytes1
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

PALOMAR COLLEGE

leukocytes involved in innate immunity hypersensitivity
Leukocytes Involved in Innate Immunity: Hypersensitivity

Basophils

Rarest of the leukocytes (<0.5%)

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

PALOMAR COLLEGE

leukocytes involved in innate immunity cytotoxicity
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.

PALOMAR COLLEGE

leukocytes involved in acquired immunity
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

PALOMAR COLLEGE

lymphocyte specialization
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

Heavy chains

 chain

PALOMAR COLLEGE

T cell

B cell

acquired immunity responses
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

PALOMAR COLLEGE

slide13
Questions??

PALOMAR COLLEGE

PALOMAR COLLEGE