OPTO 5344

Physiology & Molecular Biology

Immunology

Rachel Redfern, OD, PhD, FAAO

Rm. 244 HBSB

Reading

Chapter 3 “Immunopathology” in Pathology for the Health-Related Professions by Damjanov

“Immunology”5th Edition, by Riott, Brostoff, Male

Overview

1. Introduction to the Immune Response2. Cells of the Immune Response3. Primary vs Secondary Lymphoid Tissue4. B cells and Humoral Immunity5. T cells and Cell Mediated Immunity6. Natural Killer (NK) cells7. Complement8. Overview of Immunity9. Immunization

Discovery of Immunology

• Milk maids would get cow pox from a virus in cow utters

• Milk maids had mild symptoms

• English Physician Edward Jenner observed a protection from small pox in milk maids

• Small pox is caused by pox virus with severe symptoms…

• Very prevalent in 1700s• Multiple pocks over

entire body

• 10% adult deaths

• 1/3 child deaths

Small Pox

Jenner’s Provocative Experiment

• Then collected material from cowpox vesicles and injected it James Phipps

• 6 weeks later Phipps was inoculated with small pox and never succumbed to the disease

First vaccine

Discovery of Immunology

• Vaccination derived from latin word “vacca”

• Extensive vaccinations started 1967

• Small pox officially declared eradicated in 1980s by World Health Organization

‘immunis’ - free or exempt

Exempt from or protected against somethingdisagreeable or harmful; not susceptible to aspecific disease

To achieve protection:1.) Innate or non-acquired response

-Nonspecific

2.) Acquired or adaptive response-T and B lymphocytes-Memory! Rapid/Robust response!

Introduction

Innate Immune Response

Non-specific response

Does not improve on subsequent exposures

First line of defense

Four components:1. Physical barriers2. Physiological barriers3. Vascular system4. Phagocytic component

Physical barriers• Tightly packed

together epithelial cells

• Keratin in skin=waterproof

• Epithelial shedding

• Mucus coat

Innate Immune Response

Innate Immune Response

Physiological barriers• Fever: ↓ viral

replication• Low pH: ↓ microbes• Cough/sneeze• Blinking• Commensals• Antimicrobial

molecules• Interferon α/β

• ↓infection in neighbor cells

Interferon

• Released from virus-infected cells

• IFN binds to surface receptors on neighbor cells

• Inducing uninfected cells to synthesize antiviral proteins that interfere with or inhibit viral replication

Cytokines

Interleukins• Soluble molecules that

mediate interactions between cells

• IL-1 and IL-6: induces fever; ↑immune responseIL-8: chemotaxis for neutrophils (extravasation)IL-12: acts with IL-2 in T cell maturation

Lysozyme

Lyzozyme• Tears, saliva, in

granules of neutrophils

• Degrades cell wall

• Gram + bacteria succumbs to osmotic gradient

• Penetration=acute inflammatory response

• Increased vascular permeability

• Phagocytic cells recruited from the blood to remove invading pathogens

Vascular/Phagocytic

Pathogen Recognition

• Latin “opsono”: to prepare food for…YUM!

• Host derived opsonins

1. Complement fragments (C3b) bind to C3b receptor on immune cells

2. Antibodies bind Fc receptor on immune cells…Note antibodes are part of the adaptive immune response!

Pathogen Recognition

PRRPAMP

Opsonin

Recognizes pathogen associated molecular patterns (PAMP) on microbes

• LPS• Flagellin

Pattern recognition receptors (PRR)

• Mannose receptors: sugar on pathogens → phagocytosis

• CD14• Toll-like Receptors (TLR)

pathogen pathogen

What is an opsonin?1. C3b2. Antibodies

Immune Cell

Innate Immune Response

• Jules Hoffman for initial discoveries of Toll-like Receptors (TLR) in drosophila

• Bruce Beutler identified TLR4, the first mammalian TLR

Beutler Hoffman

• Stimulates the production of cytokines, chemokines and antimicrobial peptides

• Pattern Recognition Receptor

• Alert the immune system of infection

• Kill pathogens

Redfern and McDermott, Experimental Eye Research, 2010, 90, 679-87

Toll-like Receptors

Innate Immune Response: Review

Acquired Immune Response

• Pathogen specific

• Improves on subsequent exposure i.e. memory

•Antigen (immunogen): something that induces immune response

•Hapten: too small for immune response unless attached to larger molecule

•Epitope: 3D molecular arrangement on antigen recognized by immune system

TX size microbe antigen epitopes

• Mediated by lymphocytes: white blood cells

• B lymphocytes (B cells) produce/secrete antibody• Humoral immunity of fluid

• T lymphocytes (T cells) help B lymphocytes (B cells) produce antibody and help destroy organism/infected cells • Cell mediated immunity

• Memory cells

Acquired Immune Response

• Granulocytes

• Platelets

• Mononuclear Cells

• Dendritic Cells

• Lymphocytes

Cells of The Immune Response

Cells of The Immune Response

• All cells derived from Haematopoeitic stem cell (Bone Marrow)

• divide and into different lineages

• “colony stimulating factors” regulate the production of these cells

Cells of The Immune Response

IL-7

IL-3

Mono-CSF

• IL-3 (multi-colony stimulating factor): either lineage

• IL-7: lymphoid cells

• Granulocyte- monocyte CSF

• Monocyte CSF

• Granulocyte CSF

Granulocytes In Innate Immune Response

Neutrophils

Eosinophils

• In general, granulocytes…

• Produced in the bone marrow (7mill/min)

• 50 billion in circulation

• Life: 2-3 days

Basophils(and mast cells)

Granulocytes In Innate Immune Response

Neutrophils

Eosinophils

Basophils(and mast cells)

Neutrophils• 95% of circulating granulocytes• Multilobes nucleus (2-3)• PMN• 10-20µm across• Migrate rapidly to site of infection (C5a)• Phagocytose and destroy foreign

organisms• Myeloperoxidase (MPO) and lysozyme

Granulocytes in Innate Immune Response

• Neutrophil recognizes pathogen• PRR• Opsonins:C3b or antibodies

• Stimulates phagocytosis

• Reactive oxygen species and lysosomes enzymes, kill the pathogen

Granulocytes In Innate Immune Response

Neutrophils

Eosinophils

Eosinophils• Bilobed nucleus• Mix of large and small granules• 2-5% WBC• Most reside in connective tissue• Activated by IL-5 (secreted at infection site) • Phagocytosis of bacteria • Main function is binding to Ig coated

parasites that can not be phagocytosed• Produce major basic protein

• TOXIC!Basophils

(and mast cells)

Granulocytes In Innate Immune Response

Neutrophils

Eosinophils

Basophils• 0.2% WBC• Most reside in blood stream• Mast cells are equivalent in tissue• Produced/mature in the bone marrow→ circulation → infection site

• Release histamine• Allergen must cross link IgE

molecules bound to its surfaceBasophils

(and mast cells)

Granulocytes In Innate Immune Response

Neutrophils

Eosinophils

Mast cells• Produced in bone marrow and

mature in various sites of the body• Release histamine

• Mucosal mast cell• Connective tissue mast cells

Basophils(and mast cells)

Platelets

• Blood clotting (AKA thrombocytes)

• Involved in inflammation

• Adhere to endothelial surface of damaged blood vessel and release factors to: • ↑ capillary permeability• ↑ leukocyte recruitment

Cells of The Immune Response

• Granulocytes

• Platelets

• Mononuclear Cells

• Dendritic Cells

• Lymphocytes

Mononuclear Phagocytes CSF

• Monocyte to Macrophages (BIG!)(Blood) (tissue)

• Largest in size of the circulating WBC • Capable of phagocytosis• 2-8%• Horse shoe nucleus• Macrophages names vary on location

• Kupffer Cells in Liver• Microglia in Brain

Mononuclear Phagocytes

Innate Immune Response• Phagocytosis = destroying pathogens

• Release factors chemoattractive for other immune cells to boost immune response

• Release leukotrienes and prostaglandins to increase vascular permeability/ cell recruitment (BURNS lecture)

Acquired Immune Response• Antigen presenting cells (APCs)

- present antigen to T cells

Mononuclear Phagocytes: Acquired Immune Response

• Macrophage digests pathogen

• Some antigens are saved on MHC

• APC to secondary lymphoid tissue activates T cell that recognizes the antigen to generate an immune response

Major Histocompatibility Complex (MHC)

• AKA Human Leukocyte Antigens (1st discovered in WBC)

• Class I on ALL nucleated cells

• Class I and II on antigen presenting cells (APCs)•APC: Mononuclear cells, B cells, BV endothelial cells, dendritic cells

• Binding pockets for proteinNormal - filled with self-proteinInfection - filled with antigen from invading organism

Major Histocompatibility Complex (MHC)

MHC I• Single α chain +• β 2 microglobulin

MHC II• 2 chains: α/β

• Specific T-cell will recognize specific “foreign” antigen in MHC molecule and stimulate an immune response

MHC I MHC II

Unique to APC