THE ROAD MAP:Today- 4/24: Digestive System & Immune System (4)

4/25, 4/26, 4/29: Consultations (Image data review)

4/26, 4/29, 5/1: Group In-class Presentations

Lab Practical: 4/23 and 4/24

Final Exam: 10:30 AM May 7th, 2013 ISB 221

Individual Project Written Papers: due Friday, 5/3

The Group Project~10 minutes/presentation5‐7 slides: We are all about images‐ no words needed!Organization and clarity are important so REHEARSE!

PRESENTATION GOALS:Identify yourselves.Introduce the histological features of your organ using your paraffin images.Orient the audience: planes of section etc.Introduce the markers you used and your predictions. Use your images to demonstrate what stained.Discuss your results including problems or artifactual staining.

Anxieties Are Us: The Group Project

• Hands-on opportunities• Not Cookbook! No guarantees.• Beauty is hard to achieve.• Some folks are just plain lucky.• Life is not fair. Get used to it.• Relax! Do your best. Work hard.• Tell the story- but briefly!• Accept responsibility.• Enjoy the ride.

Possible Artifacts

KNIFE MARKS

FREEZE/THAW DAMAGE

OTHERS:Uneven StainingFolded/wrinkled sectionParticulate debrisAntibody nonspecific staining

Enteroendocrine Cells- Hormonal release and nerve activity required for coordinating ingestion with secretion and motility

With ingestion of food:Release of salivaRelease of digestive enzymesRelease of HClRelease of bile from gall bladderMotility of gastrointestinal tract

What signals might trigger release of hormones and digestive enzymes?

Stomach enteroendocrine cells release Gastrin:release from G cells is stimulated by:

1) peptides and amino acids in stomach lumen2) distention of stomach wall3) sensory inputs --> neural innervation (GRP)

- Parietal cells have gastrin receptors

Gastrin is only part of the story………….

Small intestine enteroendocrine cells release Choleocystokinin (CCK): CCK released is stimulated by: presence of H+, amino acids, and fatty acids - Pancreatic and gall bladder cells CCK receptors

- Release of bile from gall bladder into duodenum

- Release of digestive enzymes from pancreas

PANCREAS

PANCREAS: Endocrine / Exocrine Gland

http://www.uwgi.org/gut/stomach_03.asp

PANCREAS: Endocrine / Exocrine Gland

PANCREAS: Exocrine Gland

PANCREAS: Endocrine Gland

Islet of Langerhans: most numerous tail of pancreas, 2% volume

Pancreas: Islet of Langerhans

Pancreas: Endocrine Function

Cells: secretion of insulin in response to low blood glucose, causes uptake and storage of glucose into liver and skeletal muscle; diabetes mellitus Type I and II

Cells: secretion of glucagon in response to high blood glucose, causes synthesis of glucose and breakdown of glycogen in liver

Cells: secretion of somatostatin; inhibits insulin and glucagon release

GALL BLADDER

GALL BLADDER- lumen lined by simple columnar epithelium

- microvilli, tight junctions, mitochondria

- smooth muscle

- concentrates bile (Na+ actively pumped out of lumen in exchange for H+, water follows)

- stores bile until release

Choleocystokinin (CCK)

-Gall Bladder smooth muscle cells have CCK receptors

CCK RELEASE (INTESTINAL ENDOENDOCRINE CELLS)

GALL BLADDER CONTRACTION

RELEASE OF BILE INTO LUMEN OF SMALL INESTINE

FACILITATED DIGESTION OF LIPIDS

LIVERRight side, beneath diaphragmLobular“Hepatic”Functions: - Produce of bile - Process and store of nutrients- Phagocytose debris and bacteria

- Synthesize blood proteins and coagulation factors- Detoxify & inactivate drugs and toxic substances- Stores, modifies Vitamins A, D, K- Participate in iron metabolism- Modify hormones (thyroxine, growth hormone etc)

Blood Supply: Hepatic Portal SystemTO LIVER: PORTAL VEIN: oxygen poor blood; from stomach, pancreas, spleen, & intestines.

HEPATIC ARTERY: brings oxygen rich bloodIN LIVER: HEPATIC SINUSOIDS (2nd capillary bed-portal system) CENTRAL VEIN HEPATIC VEIN VENA CAVA

LIVER: Classic Hepatic LobuleHexagonal; connective tissue septaBounded by Portal Triads:

1) a branch of the hepatic artery2) a branch of the portal vein3) a bile ductule4) lymphatic vessel (not always present)

Central vein (terminal hepatic venule) in center

LIVER: Classic Hepatic Lobule bounded bt portal triads

LIVER: Portal Triad

LIVER: Portal Triad

LIVER: Hepatocytes- arranged in cords; separated by sinusoids

Perisinusoidal SpaceSPACE OF DISSE

Hepatocyte: 60% of all liver cells-polyhedral cells-microvilli: Space of Disse & bile canaliculi.- extensive ER- abundant

mitochondria

- storage granulesof glycogen

LIVER: SINUSOIDSDiscontinuous capillaries; Squamous endothelial cellsLittle or no basal lamina; Space of Disse

LIVER: SINUSOIDSKupffer Cells: protrude into sinusoids; contribute to endothelial lining; macrophages-like; remove blood cells, bacteria

Kupffer cells labeled with India Ink

LIVER: SINUSOIDSIto Cells (hepatic stellate cell):

in perisinusoidal space stores Vitamin A-> retinol to form photopigment (rhodopsin) in eyerespond to liver inflammation and injury-->

scarNORMAL LIVER LIVER INJURY

LIVER: LIVER ACINUSLiver Acinus: Correlates with blood perfusion, metabolic activity and liver pathology; oriented around afferent vascular system

LIVER: LIVER ACINUSZones correspond to distance from blood supplyZone 1: closest to arterioles, highest oxygen, 1st toxin exposure, necosis due to toxins, first to regenerateZone 3: farthest from arterioles, poorest supply of

oxygen, necrosis due to ischemia

LIVER: BILE PRODUCTIONBile Canaliculus: channel between adjoining

hepatocytes carries bile to bile duct

LIVER: BILE PRODUCTION

Flow of bile is opposite that of blood flow

LIVER: PORTAL LOBULEPortal Lobule: Region of bile production drained by axial bile duct

Lymphatic System

- monitor body surfaces and internal fluids for antigens and materials for removal

- react to potentially harmful substances

Lymphatic Tissues

- Concentrated nearrespiratory tract

digestive tractreproductive tract

Antigen: foreign substance

Nonspecific Inflammatory Response

Mast cells-Histamine release-Vasodilation (increase capillary permeability)

Neutrophils-enzymatic digestion of virus

Macrophages-cytokine release-phagocytosis-antigen presentation

Specific Responses to Antigen Exposure:

Antigen-Presenting Cells (APCs):-APCs include: macrophages and B-

lymphocytes

1) endocytose and degrade antigens

2) display a portion of the antigen coupled to Major Histocompatibility Complex (MHC) II

molecules and on cell surface

3) activate other immune cellsHumoral Immunity Cell-mediated ImmunityAntibody Production Killing of Infected Cells

Humoral Immunity: Antibody Production

• Stimulation of B Lymphocytes (B cells)

• Antigen processing & presentation: B cells (MHC II)

• Stimulation of CD4 Helper T lymphocytes

• Production of Interleukins --> stimulate B cells

• B cell Proliferation --> Plasma cells & Memory cells

See also Figure 14.6 in Textbook re: CD40 and CD40L

Interleukins (ILs)

Humoral Immunity: Antibody Production

B-lymphocytes differentiate to form:• Plasma Cells: produce antibodies against a

single epitope1st exposure--> IgM2nd exposure--> IgG

• Memory cells: circulate for future encounters with antigen

Humoral Immunity: Antibody Production

Classes of Antibodies

With Second Exposure to Antigen: Activation of Memory Cells specific for AntigenDifferentiate into Plasma Cells: produce IgG antibodyWith Secondary Exposure to Antigen:

immune response is fastermore antibody is produced more rapidlyantibodies bind antigen more strongly

Binding of Antibodies to Antigens Inactivates Them

Macrophage engulfs, processes & presents antigen

Stimulation of CD4 Stimulation of CD8 Helper T Lymphocytes Cytotoxic T Lymphocytes

MHC II MHC I

Release of Interleukin 2 ProliferationKilling of INFECTED cells

Cell-Mediated ImmunityCytotoxic (CD8+) T-lymphocytes attack and destroy virus-infected cells

granzymes

1)Macrophage presents antigen to CD4+ and CD8+ T cells2)IL2 stimulates CD4+ and CD8+ proliferation3)CD8+ T cells recognize virus-infected cells (MHC I)4)CD8+ release granzymes plus5)Infected cells die by apoptosis

Cell-Mediated Immunity:Cytotoxic CD8 T-lymphocytes

Cytotoxic T Lymphocytes:- bind to target cell- exocytosis of granules of perforin and granzymes

- Perforins insert into target cell membrane

- Granzymes, serine proteases,

enter cell and cause cell death (apoptosis ) via activation of precursors of caspases.

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CTL.htmlhttp://sprojects.mmi.mcgill.ca/immunology/Perforin.JPG

Natural Killer Cells: - recognize virus-infected or cancer cells- activated by antibody binding to Fc receptor- release perforin and granzymes, activate Fas- results in apoptosis (cell death)

Lymphatic Tissue and OrgansLymphatic Vessels

-more permeable than blood vessels-antigens gain entry, are carried to lymph nodes

Lymph Nodes-at points of

convergence of lymphatic vessels Function:

-nonspecific filtering-maximize interaction

between APCs and antigens

Capsule

Afferent vessels

Hilum

Efferent vessels

ArteryVein

Lymphocyte Circulation: enter node from blood & lymph

vessel

LYMPH NODE

Lymph Node

What is the structure of the lymph node?

What is the pathway of lymph and lymphocyte movement through the node?

What is the pathway of blood movement through the node?

What cellsand specialized structers contribute to lymph node function?

Lymph Node Compartments Capsule Cortex

-lymphatic nodules B lymphocytes

Deep Cortex -T lymphocytes

Medulla

CapsuleCortex

Deep Cortex

Medulla

http://www.nature.com/ni/journal/v7/n4/fig_tab/ni1330_F1.html

Lymph Node Cortex Lymphatic nodules (follicles)

Primary: - Naive B cells - Memory B cells

Secondary:–Inactive B cells - periphery–Activated B cells- germinal center–Follicular dendritic cells

Cortex: Lymphatic Nodules or Follicles

Follicular Dendritic Cells (arrows below)

• Found in germinal centers

• have Fc receptors

• bind antigen/antibody complexes

• processes contact B-lymphocytes

Dendritic Cells

-Antigen-presenting cells

-Activate T-cells

-Dendritic cells enter lymph mode in lymphatic vessels

-Locate in periphery of Follicle in lymph node

http://www.biken.osaka-u.ac.jp/COE/eng/project/images/fig-hirata-jpg.jpg

Lymph Node Deep Cortex (2)

• No Lymphoid nodules (5)• Almost all cells are T lymphocytes

• High endothelial venules

Lymph Node Medulla (3)• Medullary cords (4)• Medullary sinuses• B lymphocytes• Plasma cells• Macrophages www.histol.chuvashia.com/atlas-en/lymphoid-en.htm

Medulla

Some lymphocytes:- Enter node in

lymph

Most lymphocytes:- enter node through High endothelial venules (HEVs)- migrate to the

superficial cortex and follicles

- proliferate after activation- otherwise

reenter circulation

High Endothelial Venule- Plump endothelial cells- Cell adhesion molecules- Promote migration of lymphocytes from blood into node (extravasation)- Mainly in deep cortex- Release of chemokines

http://mcb1.ims.abdn.ac.uk/teaching/Honsdocs/Miyasaka.pdf

Lymphocyte movement through High

Endothelial Venules

“Selectins on a lymphocyte's microvilli cause it to slightly stick to endothelium and it slowly rolls along until integrin receptors at the tips are activated by chemokine to stick more firmly. The lymphocyte polarizes and begins squeezing into the space between two or more endothelial cells.”http://www.geocities.com/CapeCanaveral/Hangar/1962/page3.html#L02

The Fibroblastic Reticular Cell Conduit (FRCC)

- channels from HEVs in deep cortex; formed by fibroblastic reticular cells

- a conduit for movement of soluble molecules, such as chemokines and antigens, between the cortex and deep cortex

- channel contains ECM (collagens and proteoglycans) & adhesion proteins that promote T- and B-cell movement

Nature Reviews Immunology (Vol 3, No. 11, pp 867-878 (2003)

Lymphocytes migrate from blood or lymph to node- B cells migrate to superficial cortex- T cells migrate to deep cortex

After activation:B lymphocytes--> plasma cellsPlasma cells ->medullary cords-> release

antibodyMemory cells may return to the blood or

lymph

Lymphocyte Movement