Module 1

Lymphatic System

Lymphoid organs
Vessels with lymph (WBC)
From capillaries to surrounding tissues

Circulatory System

Lymph origin and end
Lymph enter at heart

Immune System

Cells travel between lymphatic and circulatory systems
Cells bind antigens
Eliminate in lymph nodes

Primary Lymphoid Organ

Mature into immunocompetent cell

Immunocompetent Cell

Mature cell
Recognize self and non-self
Mediate immune response

Primary Lymphoid: Bone Marrow

Yellow and red tissue
Hematopoietic cells

Bone Marrow Location

Central bone cavity

Red Bone Marrow Function

Immunity
Hematopoiesis
B-cell development

Yellow Bone Marrow Function

Leukocyte development
Fat and cartilage production

Primary Lymphoid: Thymus

Flat
Cortex and medulla (bi-lobed)
Contain thymocytes (T-cells), epithelial cells, dendritic cells, macrophages

Thymus Location

Above heart

Thymus Function

T-cell development and maturation

Secondary Lymphoid Organs

Activate into effector cell

Effector Cell

Mature cell
Mediate immune response
After antigen interaction

Secondary Lymphoid: Lymph Nodes

Small and bean-shaped
Numerous
3 regions: Cortex, Paracortex, Medulla
Contain lymphocytes (B and T cells), dendritic cells, macrophages

Lymph Node Location

Along lymphatic vessels

Lymph Node Function

Filter lymph
First structure antigens encounter

Secondary Lymphoid: MALT

Mucosal Associated Lymphoid Tissue
Tissue in sites open to outside
Digestive, respiratory, urogenital
Diff immune cells by location

MALT: BALT

Bronchus-Associated Lymphoid Tissue
Lungs and bronchus

MALT: GALT

Gut-Associated Lymphoid Tissue

MALT: Lamina Propria of Intestinal Villi

Connective tissue in small intestine lumen

MALT: Peyer's Patches

In ileum

MALT: Tonsils

In pharynx

MALT: Appendix

In cecum (colon)

MALT Function

Initiate immune response
Detect antigens

Secondary Lymphoid: Spleen

Large oval
White and red pulp

Spleen White Pulp

Contain macrophages, lymphocytes, T-cells, B-cells, RBCs

Spleen Red Pulp

Cords of Billroth (fibrils, connective tissue, monocytes, macrophages)
Splenic sinuses with blood

Spleen Location

Left abdominal cavity

Spleen White Pulp Function

Develop immune responses in blood

Spleen Red Pulp Function

Filter blood

Immune System Function: Discrimination

Self and non-self
Initiate response against non-self
Immune cells present Major Histocompatibility Complex I and II (MHC)
Scan for abnormal MHC proteins on cells

Immune System Function: Eliminate

Initiate immune response
Eliminate non-self

Innate Immunity

First line of defence
Physical, soluble, cellular barriers

Innate Immunity: Function

Prevent pathogen entry
Immediate response
Non-specific recognition

Adaptive Immunity

Cells and soluble components
Antibody mediated
Humoral Immunity: B-cells
Cell-Mediated Immunity: T-cells

Adaptive Immunity: Functions

Delayed response
Specific recognition and response
Immunological memory

Lymphoid Tissue Evolution

GALT -> Thymus and spleen -> Lymphocyte generation in bone marrow -> Lymph nodes

Innate Immunity Evolution

Vertebrates, invertebrates, plants

Adaptive Immunity Evolution

Vertebrates
More complex organisms

Hematopoietic Stem Cells (HSC)

Produce immune and blood cells
Erythrocytes, leukocytes, platelets
Self-renew
In fetal liver and bone marrow

HSC: Pluri/Multipotent

Differentiate into diff cell types
Committing to lineage = no self-renewal

Immune Lineage: Myeloid Progenitor

Innate immunity
Granulocytes (neutrophil, eosinophil, basophil, mast cell)
Monocytes (macrophage)
Erythrocytes
Thrombocytes (platelets)

Immune Lineage: Lymphoid Progenitor

Adaptive immune system cells
B-Cells (effector plasmocyte, memory B-cell)
T-Cells (helper T-cell, cytotoxic T-cell, memory T-cell)
Natural Killer Cells (innate)

Dendritic Cell

Phagocyte
Innate and adaptive immunity
From myeloid or lymphoid cells
Many subsets

Dendritic Cell Functions

Phagocytosis
Antigen presenting cell (to adaptive)
Communicate between innate and adaptive

Erythrocyte

Myeloid
From hematopoiesis

Thrombocyte

Myeloid
Platelet
From hematopoiesis

Thrombocyte Functions

Coagulation, wound healing, fibrinolysis
Combat microbial threats
Promote innate effector cell functions
Modify antigen presentation
Enhance adaptive responses

Monocyte

Myeloid
Phagocyte
In blood

Macrophage

Myeloid
Phagocyte
Monocyte in tissues
Increase intracellular structures

Macrophage Functions

Better phagocytosis
APC

Macrophage: Pseudopodia

Temporary cell membrane projections
For motility

Macrophage: Phagosome

Vacuole containing phagocytosed particles

Macrophage: Lysosome

Vacuole containing digestion enzymes
Form phagolysosome with phagosome

Mast Cell

Myeloid
Granulocyte
In tissues
Large granules with histamine and other active substances

Mast Cell Function

Histamine: allergy

Neutrophil

Myeloid
Most abundant leukocyte
Granulocyte
Polymorphic nucleus
Lifespan of few days
Granules with lytic enzymes

Neutrophil Functions

Bacteria phagocytosis
First at inflammation site

Neutrophil: Peroxidase

Lytic enzyme
Substrate oxidation by H2O2

Neutrophil: Lysozyme

Lytic enzyme
Destroy bacterial cell wall

Basophil

Myeloid
Granulocyte (least common)
Polymorphic nucleus
Largest granules with histamine and heparin

Basophil Functions

No phagocytosis
Histamine: Allergy
Heparin: Inhibit blood coagulation

Eosinophil

Myeloid
Granulocyte
Phagocytosis
Polymorphic nucleus

Eosinophil Functions

Granules defend against and damage parasitic membranes

Natural Killer Cell

Lymphoid
Innate
Granular lymphocyte
No antigen-specific receptors

NK Cell Functions

Recognize and destroy abnormal cells

NK Cell: Perforin

Protein in granules
Create lesion in membrane

NK Cell: Granzymes

Protease in granules
Induce programmed cell death

T-Cell

Lymphoid
T lymphocytes
Produced in bone marrow
Mature in thymus
Cell-mediated immunity
Non-phagocytic
For changed body cells

T-Cell: Specificity

Surface T-cell receptors (TCR)
TCR recognize specific processed antigen

T-Cell: Diversity

Recognize diff antigen

Helper T-Cell

Surface CD4 molecule
Activated by antigen-MHC class II

Helper T-Cell: Effector Cells

Activate other immune cells (B-cells, cytotoxic T-cells, macrophages)

Helper T-Cells: Memory Cells

Antigen recognition

Cytotoxic T-Cell

Surface CD8 molecule
Activated by antigen-MHC class I

Cytotoxic T-Cells: Effector Cells

Monitor body cells
Eliminate cells with MHC class I (virus, tumors)

Cytotoxic T-Cells: Memory Cells

Long term antigen recognition

B-Cell

Lymphoid
B lymphocytes
Produced and mature in bone marrow
Humoral immunity
Non-phagocytic
For foreign molecules

B-Cell: Specificity

Surface B-cell receptors (BCR)
BCR recognize specific non-processed antigen

B-Cell: Diversity

Recognize diff antigens

B-Cells: Plasmocytes

Plasma cells
Effector cell
No interaction with antigen for activation
Produce and secrete antibodies

B-Cells: Memory Cells

Antigen recognition
Same BCR as mother cell

Bacteria

Unicellular
Prokaryotes
Circular, double stranded DNA
Less proteins

Bacteria Ex

Cholera

Viruses

Not organism
Rely on host cell for metabolism and reproduction
Double/single stranded DNA/RNA
Capsid protein coat around genome
Outer lipid envelope

Virus Ex

Influenza

Fungi

Eukaryotes
Heterotrophic
Rigid cellulose/chitin cell wall
Spore reproduction

Fungi: Divisions

Mold: Multicellular
Yeast: Unicellular

Fungal Infection

Weak immune system
Taking antibiotics

Fungi Ex

Vaginal yeast infection

Protozoa

Eukaryotes
Unicellular
Heterotrophic
No cell walls
Rapid and flexible movement

Protozoa Ex

Malaria

Helminths

Parasitic worms
Multicellular
Differentiated tissues
Treatment drugs toxic to human cells

Helminth Ex

Schistosomiasis

Prions

Proteins
Misfolding cause CNS disorders
Resist degradation
Accumulate in and degrade brain tissue

Prion Diseases

Bovine spongiform encephalopathy
Creutzfeldt-Jakob disease