Immunology in Endocrinology

Immunology in Endocrinology

Dr. Jim Johnson, Ph.D. Assistant Professor, Dept. of Cellular and Physiological Sciences and Dept. of Surgery,University of British Columbia 5358 Life Sciences Building Lab W ebsite: www.diabetes.ubc.caOffice: (604) 822-7187 E-mail: jimjohn@interchange.ubc.ca

Outline and Objectives:

1) Immunology basics - self versus non-self

2) Immunology basics - specific cell types

3) Immunology basics - T-cell activation

4) Immunology in Endocrinology - Other diseases

5) Immunology in Endocrinology - Type 1 diabetes

6) Immunology in Endocrinology - Type 2 diabetes

Immunology in Endocrinology

Immunology basics - Self versus non-self

‘Immunity’ refers to the global ability of the host to resist the

predation of microbes that would otherwise destroy it. Immunity

has many facets, but the greatest dichotomy separates adaptive

immunity (‘acquired immunity’) from innate immunity (‘natural

immunity’ or ‘innate resistance’).

A key element of immunity is the recognition of ‘self’ and of ‘non-

self’. Errors in this recognition lead to autoimmune diseases,

likely type 1 diabetes.

A complex array of cell types control this process.

Immunology basics - Innate vs. Adaptive Immunity

The immune system is typically divided into two categories--innate and

adaptive--although these distinctions are not mutually exclusive.

Innate immunity

Innate immunity refers to nonspecific defense mechanisms that come into

play immediately or within hours of an antigen's appearance in the body.

These mechanisms include physical barriers such as skin, chemicals in the

blood, and immune system cells that attack foreign cells in the body. The

innate immune response is activated by chemical properties of the antigen.

Adaptive immunity

Adaptive immunity refers to antigen-specific immune response. The adaptive

immune response is more complex than the innate. The antigen first must be

processed and recognized. Once an antigen has been recognized, the

adaptive immune system creates an army of immune cells specifically

designed to attack that antigen. Adaptive immunity also includes a "memory"

that makes future responses against a specific antigen more efficient

Immunology basics - Cellular vs. Humoral Immunity

Questions or discussion

?Where are the ‘weak links’ in the immune system?

Immunology basics - Specific cell types

Immunology basics - Hematopoietic stem cells

Questions or discussion

?What is the proof, in the lab or in the clinic, that these cells are truly stem cells?

Immune cell types

Immune cell types

Red blood cell

Monocyte

Neutrophil

Platelet

Immune cell types - B cells

B lymphocytes (from Bursa of Fabricius)

These cells are major antibody producers.

•Plasma B cells are actively producing

antibodies.

•Memory B cells respond quickly following

a second exposure to a specific antigen

Immune cell types - T-cells

T-lymphocytes - mature in the thymus

These cells are a major mediators of cell-mediated immunity.

T-lymphocytes - T-cell receptor

T-lymphocytes talk with antigen-present cells using the T-cell receptor.

The signal from the T cell complex is enhanced by

simultaneous binding of the MHC molecules by a co-receptor.

The co-receptor on helper T cells is CD4, which exclusively

binds the class II MHC.

The co-receptor on cytotoxic T cells is CD8, which is specific

for class I MHC.

The co-receptor not only ensures the specificity of the TCR for

the correctly-presented antigen but also allows prolonged

engagement between the antigen presenting cell and the T cell

and recruits essential molecules (e.g., LCK) inside the cell that

are involved in the signaling of that activated T lymphocyte.

T-lymphocytes - T-cell activation

T-lymphocytes - T-cell activation signalling pathways

T-cell activation - The role of Ca2+ signals

A cytosolic Ca2+ signal is an essential early event in T cell activation.

T-cell activation - The immunological synapse

T-cells ‘lock’ onto antigen presenting cells via a ‘synapse’.

T-cell activation - The immunological synapse

T-cells ‘lock’ onto antigen presenting cells via a ‘synapse’.

T-cell activation signals proceed

the formation of the ‘synapse’.

T-cells - Immunosuppressant drugs block T-cell activation

Islet transplant drugs:

Tacrolimus (FK506) - blocks calcineurin

Sirolimus (rapamycin) - blocks mTORDaclizumab - antibody against IL-2R

T-cell activation - Shape changing

T-cell activation - signals controlling cytoskeleton reorganization

Questions or discussion

?Any questions on T-cell activation. What types of signal coding are involved?

Immune cell types - Subsets of T-cells

Helper T cells - Once activated, they divide rapidly and secrete small proteins called cytokines

that regulate or "help" the immune response.

Cytotoxic T cells - Destroy virally infected cells and tumor cells, and are also implicated in

transplant rejection. These cells are also known as CD8+ T cells, since they express the CD8

glycoprotein at their surface. Through interaction with helper T cells, these cells can be

transformed into regulatory T cells.

Memory T cells - A subset of antigen-specific T cells that persist after an infection. They quickly

expand to large numbers of effector T cells upon re-exposure to their cognate antigen, thus

providing the immune system with "memory" against past infections. Memory T cells comprise two

subtypes: central memory T cells (TCM cells) and effector memory T cells (TEM cells). Memory

cells may be either CD4+ or CD8+.

Regulatory T cells - (a.k.a. suppressor T cells). These are crucial for the maintenance of

immunological tolerance. Their major role is to shut down T cell-mediated immunity toward the end

of an immune reaction and to suppress auto-reactive T cells that escaped the process of negative

selection in the thymus. Naturally occurring Treg cells can be distinguished from other T cells by

the presence of an intracellular molecule called FoxP3. Mutations of the FOXP3 gene can prevent

regulatory T cell development, causing fatal autoimmune disease.

Natural Killer T cells - bridges the adaptive immune system with the innate immune system. NKT

cells recognize glycolipid antigen presented by a molecule called CD1d, rather than MHC. Once

activated, these cells initiate both cytokine production and release of cell killing molecules.

T cells - possess a distinct TCR on their surface. 5% of all T cells.

Autoaggressive T cells - characterized by CD40 expression, which is typically is associated with

antigen-presenting cells. Th40 cells are expanded in autoimmune subjects.

Regulatory T cells - Help suppress responses when appropriate

This subset of T cells is identified by the expression of CD4, CD25 and FoxP3.

Regulatory T cells - Help suppress responses when appropriate

Mechanism of bystander suppression. Tregs that are activated by DCs in an

antigen-specific fashion release IL-10. Once released, IL-10 inhibits immunereactions not only against the initial antigen (dot) but also against otherantigens (square, triangle) in a nonspecific fashion.

Questions or discussion

?Do antigen-specific Tregs have potential therapeutic value?

Immune cell types - Natural killer cells

Natural killer cells

These cytotoxic cells are a major

component of the innate immune

system.

They release granules of perforin

and granzyme that cause cells to

undergo apoptosis.

Immune cell types - Macrophages

Macrophage (greek for big eaters)

These cells roam tissues looking for ‘foreign

cells’ or dead cells.

They also display antigens via MHC class II.

Immune cell types - Neutrophils

Non-segmented neutrophils are younger.

Neutrophils are granulocytes, filled with neutrally-staining granules which

contain enzymes that help the cell to kill and digest microorganisms it has

engulfed. The neutrophil has a lifespan of about 3 days.

Immune cell types - Neutrophil targeting and tissue invasion

Immune cell types - Neutrophils communicate with other cells

Through cell–cell contact and secretedproducts, neutrophils recruit andactivate monocytes, dendritic cells

(DCs) and lymphocytes, and productsof monocytes, macrophages and Tcells activate neutrophils. Tissuemacrophages ingesting apoptotic

neutrophils produce less interleukin-23 (IL-23). IL-23 triggers T cells insecondary lymphoid tissues toproduce IL-17. IL-17 triggers stromal

cells in the bone marrow to producegranulocyte colony-stimulating factor(G-CSF). G-CSF promotesproliferation of neutrophil precursors

and release of neutrophils into thecirculation (see text for references).BLyS, tumour-necrosis factor-relatedligand B-lymphocyte stimulator;

CXCL12, CXC-chemokine ligand 12;IFN, interferon-; TNF, tumour-necrosis factor.

Neutrophils - Release serine proteases with specific targets

Neutrophils - A movie

Questions or discussion

?What dangers are there for people who are ‘neutropaenic’?

What could cause this?

Autoimmune diseases - A partial list

•Type 1 diabetes (possibly also type 2 diabetes)

•Graves’ diseases

•Hashimoto’s diseases

•Systemic Lupus Erythematosus (SLE)

•Multiple sclerosis

•Rheumatoid arthritis

Autoimmune diseases - Graves’ and Hashimoto’s diseases

Chronic thyroiditis (Hashimoto's disease) is a

slowly developing persistent inflammation of

the thyroid which frequently leads to

hypothyroidism, a decreased function of the

thyroid gland. Middle-aged women are most

commonly affected.

Graves' disease is a thyroid-specific autoimmune

disorder in which the body makes antibodies to

the thyroid-stimulating hormone receptor (TSHR),

leading to hyperthyroidism, or an abnormally

strong release of hormones from the thyroid gland.

Autoimmune diseases - Systemic lupus erythematosus

Systemic Lupus Erythematosus (SLE) is a chronic, usually life-long, potentially fatal

autoimmune disease characterized by unpredictable exacerbations and remissions with

variable clinical manifestations. In Lupus SLE there is a high probability for clinical

involvement of the joints, skin, kidney, brain, lung, heart, serosa and gastrointestinal tract.

African-Americans and Asians are disproportionately affected. There is a female to male sex

bias of 8:1.

Autoimmune diseases - Multiple sclerosis

Multiple sclerosis is a central nervous system disorder marked by decreased

nerve function with initial inflammation of the protective myelin nerve covering

and eventual scarring. Symptoms and severity of symptoms vary widely and may

progress into episodes of crisis alternating with episodes of remission.

Autoimmune diseases - Rheumatoid arthritis

Rheumatoid arthritis is a systemic autoimmune disease which initially attacks the

synovium, a connective tissue membrane that lines the cavity between joints and

secretes a lubricating fluid.

Questions or discussion

?What do autoimmune diseases have in common? What does this tell us?

Autoimmune diseases - Type 1 diabetes

Type 1 diabetes is one of the most common and most expensive autoimmune

diseases.

Frequent urination

Excessive thirst

Unexplained weight loss

Extreme hunger

Sudden vision changes

Tingling or numbness in hands or feet

Feeling very tired much of the time

Very dry skin

Sores that are slow to heal

More infections than usual

Nausea, vomiting, and stomach pains

Type 1 diabetes - Diagnosis

Type 1 diabetes - A model autoimmune disease

Type 1 diabetes:

1) is associated with marked infiltration

of T-lymphocytes.

2) can be transferred from one mouse to

another by auto-reactive T-cells.

3) can be impeded (in mice) by

treatments that suppress the immune

system

Insulin / CD3+ T-cells

Type 1 diabetes - a model autoimmune disease

Type 1 diabetes - Natural history of disease progression

Type 1 diabetes - Genetic susceptibility IDDM 1 - HLA genes

•In humans, the 3.6-Mb (3 600 000 base pairs) MHC region on chromosome 6 contains 140

genes. About half have known immunological functions.

•MHC class II molecules on the surface of antigen-presenting cells display a range of peptides

for recognition by the T-cell receptors of CD4+ T helper cells.

•Thus, MHC class II molecules are central to effective adaptive immune responses, but

conversely, genetic and epidemiological data have implicated these molecules in the

pathogenesis of autoimmune diseases.

•The strength of the associations between particular MHC class II alleles and disease render

them the main genetic risk factors for autoimmune disorders such as type 1 diabetes.

Type 1 diabetes - genetic susceptibility IDDM 1 - HLA genes

MHC Class 1 MHC Class 2

Type 1 diabetes - genetic susceptibility IDDM 1 - HLA genes

Type 1 diabetes - genetic susceptibility IDDM 2 - insulin gene

Chromosome 11

The IDDM2 locus contributes about 10% of the type 1 diabetes risk that is synergistic with HLA.

The IDDM2 locus contains a sequence of repeated DNA called a variable number tandem repeats (VNTRs).

There are three classes of VNTR in the insulin gene:

• Class I has alleles that range from 26 to 63 repeat units - common in Caucasians (70% of alleles), confers risk.

• Class II has alleles that average around 80 repeat units - rare.

• Class III has alleles ranging from 141 to 209 repeat units - protective.

The presence of at least one class III allele is associated with a 3-fold reduction in the risk of type 1 diabetes,

compared with common I/I homozygote genotype. Because the VNTR occurs in a non-coding region, its

influence on diabetes risk cannot be attributed to an alteration of the protein sequence. The VNTR probably

affects the transcription of the insulin gene. Class III alleles are associated with 15-30% lower INS mRNA in the

pancreas, but higher INS mRNA in the thymus.

The thymus helps train the developing immune system by deleting autoreactive T cells. Because the longer

VNTRs cause more insulin to be produced in the thymus, the detection and deletion of autoreactive T cells may

be more efficient. This improved immune tolerance to insulin would lessen the risk of a future onset of type 1

diabetes caused by anti-insulin antibodies.

Questions or discussion

?Is there an alternative hypothesis for the effects of the insulin VNTR?

Type 1 diabetes - Human susceptibility genes IDDM 3-18

Type 1 diabetes - Genetically susceptible NOD mice

Mouse diabetes genes are denoted with lower case (i.e. iddm1-27).

Hu

ma

nN

OD

mo

use

Type 1 diabetes - Hundreds of cures for NOD mice

Questions or discussion

?Do any of these work in humans? What does that tell us?

Type 1 diabetes - Autoantibodies

Most, if not all, are normally found inside beta-cells.

Type 1 diabetes - Autoantibodies to a zinc transporter, ZnT8

Slc30A8 is also a type 2 diabetes susceptibility gene… interesting…

Type 1 diabetes - Insulin is an early autoantigen in humans

Antibodies to insulin are usually the earliest to be detected in high-risk infants.

Type 1 diabetes - Insulin is a ‘primary’ autoantigen in NOD mice

Type 1 diabetes - Triggers?

Examples:

• Viruses

• Cow’s milk (insulin)

Type 1 diabetes - Mechanisms of -cell death

Pancreatic beta-cells are specifically targeted in type 1 diabetes.

Type 1 diabetes - Mechanisms of -cell death

Cytokines play an important role in

beta-cell death in type 1 diabetes.

Type 1 diabetes - Mechanisms of -cell death

Type 1 diabetes - Mechanisms of -cell death

Type 1 diabetes - Mechanisms of -cell death

Questions or discussion

?Do any of these work in humans? What does that tell us?

Type 2 diabetes - Possible role for the immune system?

Ramlo-Halsted et al.

Type 2 diabetes - Possible role for the immune system?

Type 2 diabetes - Possible role for the immune system?

http://www.hsph.harvard.edu/GSH-LAB/tnf-ins.html

Type 2 diabetes - Resident macrophages are found in islets

Islet Macrophage

Type 2 diabetes - Macrophages are abundant in T2D islets

Questions or discussion

?If type 2 diabetes is affected by systematic inflammation, how can we use

this information?