Lymphatic & Immune System

Lymphatic/ immune system duty

• to assist in circulating body fluids & helps defend against disease-causing agents

4 parts of the lymphatic system:

1. Lymp

2. Lymphatic vessels

3. Lymphoid tissues & organs

4. Lymphocytes, phagocytes, & other immune system cells

Lymph definition

• a fluid similar to plasma

• Does NOT have plasma proteins

Lymphatic vessels (lymphatics) definition

Network that carries lymph from peripheral tissues to the venous system

Lymphoid tissues & lymphoid organs are found:

Throughout the body

4 functions of the lymphatic & immune system:

1. Drain excess interstitial fluid

2. Lymph

3. Transport dietary lipids

4. Carry out immune responses

4 functions of lymphatic & immune system: Drain excess interstitial fluid

• 3 liters of interstitial fluid needs to be reabsorbed; lymph system uses WBCs to “clean” fluid & returns it to the blood streams

4 functions of lymphatic & immune system: Lymph

When interstitial fluid enters system it becomes this

4 functions of lymphatic & immune system: Transport dietary lipids

• when fat is absorbed in GI tract it & fat soluble vitamins are transported in the lymph system

4 functions of lymphatic & immune system: Carry out immune response

• immune system is contained in the lymphatic system

Lymphatic capillaries function

• for collection only, NOT exchange

• Are closed at one end, contain valves, one way flow into capillary & back to heart

• Have larger diameters & thinner than blood capillaries

Location of lymphatic capillaries

• spaces between cells, run w/ blood capillaries

Endothelial cells function

• important in maintain one way flow into lymphatic capillaries

Anchoring filaments function

• used to keep lymphatic capillaries open, prevent collapse

Lacteals function

• specialized lymphatic capillaries in small intestine to carry lipids from diet

Chyle function

• specialized white lymph (contains fat) from lacteals

Lymphatic flow order:

1. Blood capillaries (blood)

2. Interesting space (fluid)

3. Lymphatic capillaries (lymph)

4. Lymphatic vessels (lymph)

5. Lymphatic ducts (lymph)

6. Subclavian veins (blood)

The lymphatic system is very LEFT SIDED, the lower body all drains into what duct?

Thoracic duct

Left subclavian vein consists of:

• Thoracic duct

  • Left jugular trunk (head & neck)

  • Left subclavian trunk (arm)

  • Left bronchomediastinal trunk (chest)

Right subclavian vein consists of:

• right lymphatic duct

  • Right jugular trunk

  • Right subclavian trunk

  • Right bronchomediastinal trunk

Where do stem cells divide & develop? (Factory)

1. Red bone marrow

2. Thymus gland

Where does the immune response occur? (Battle field)

1. Lymph nodes

2. Spleen

3. Lymphatic nodules

Red bone marrow

Produces hemocytoblasts—> produces B cells & PRE- T cells

Thymus gland (lymphatic system)

Matures (educates) T cells

Lymph nodes- immune response

Lymph will flow from 1 node to the next for immune response

Lymph nodes overview:

1. A/b 600 located along lymph vessels

2. Concentrated in: breast, axillary, & groin

3. Divided into:

   • Capsule

   • Outer

   • Inner

   • Medulla

Capsule (lymph nodes)

Outer covering

Outer cortex (lymph nodes)

Contains mostly B cells & macrophages

Inner cortex (lymph nodes)

Contains mostly T cells

Medulla (lymph nodes)

B cells, antibodies from plasma cells, & macrophages

Lymph Node Flow

1. Afferent lymphatic vessel (into node)

2. Subcapsular sinus

3. Trabecular sinus

4. Medullary sinus

5. Efferent lymphatic vessel (out of node)

   • Designed to pass lymph by different WBCs

Metastasis definition

• secondary tumor sites can be predicted according to the direction of lymph flow from the primary tumor site

  • Node is NOT tender like inflamed nodes

  • Use dye to detect central node for BIOPSY

Spleen

• largest single mass of lymphatic tissue

• LOCATION: left side between stomach & left kidney

Capsule (Spleen)

• outer covering, contains hilus (splenic arteries, veins & efferent lymph vessels)

Parenchyma (spleen)

• center of spleen, 2 tissues

  • White Pulp & Red Pulp

White Pulp (parenchyma of spleen)

• lymphatic tissue, lymphocytes, & macrophages are located around a central artery (branches of splenic artery)

Red Pulp (parenchyma of spleen)

• blood filled venous sinuses, contains RBCs, leukocytes, & plasma cells

3 functions of Red Pulp

1. Remove worn out RBCs

2. Store platelets (1/3 of body total)

3. Produce blood cells

   • Blood enters white pulp where it is “phaged” (gets ride of blood born pathogens)

   • Then into red pulp—> then into splenic veins

Thymus gland overview:

• sits on top of heart, covered by a capsule, larger in kids (70g vs 3g in adults)

• Cortex

• Medulla

• Epithelial cells

Cortex (of thymus gland)

• pre T cells (immature cells) collect here from red bone marrow, this is where they will mature

Medulla (of thymus gland)

• contains more mature T cells

Epithelial Cells (of thymus gland)

• helps “education” of T cells by “positive selection”, only 20% make it, T cells leave thymus to collect in spleen, lymph nodes & lymphatic tissue

Lymphatic nodules

• spread through different areas of the body

• Egg-shaped masses of lymphatic tissue not covered by a capsule

Tonsils

• lymphatic nodules in oral cavity

Different types of tonsils

1) pharyngeal- posterior wall of nasopharynx

2) palatine- back side of oral cavity (removed)

3) lingual- back base of tongue

Malt

Mucosa-associated lymphatic tissue

• spread through out connective tissue of GI tract, urinary & reproductive systems

Peyer’s patch

• lymphoid tissues associated w/ the digestive system

• Clustered deep to intestinal epithelial lining

Appendix

• mass of fused lymphoid nodules

Innate Defenses overview

• present at birth

• Offers immediate protection against a variety of pathogens

• Functions the same way regardless of the type of invader

First line of defense definition

• physical & chemical barriers discourage pathogens from penetrating the body & causing disease

Skin (epidermis)- first line of defense

• provides a tough physical barrier

Mucous membranes- first line of defense

traps many microbes & foreign substances

Lacrimal apparatus- first line of defense

• provides tears to wash away irritants to the eyes

Saliva- first line of defense

• reduces growth of microbes in the mouth

Urine flow- first line of defense

• cleanses the urethra

Gastric juice- first line of defense

• strong acidity destroys many pathogens

Internal antimicrobial proteins- second line of defense

• found in blood & interstitial fluid, discourages growth of microbes

Interferons- second line of defense

• prevent viruses from replicating

Complement system- second line of defense

• found in blood plasma & plasma membranes, when activated enhances immune reactions- stimulation of inflammation, attraction of phagocytes, enhancement of phagocytosis by complements working w/ antibodies, & destruction of target cell membranes by complements proteins

Transferrins

• iron binding proteins, reduced iron needed for bacterial growth

Natural killer cells- second line of defense

• 5-10% of lymphocytes, attack, cells that display abnormal plasma membrane proteins (MHC)

Phagocytes- second line of defense

• specialized cells that ingest microbes & other cellular debris

  • Ex: (neutrophils & macrophages)

Chemotaxis

• chemically stimulated movement of phagocytes

Adherence

• attachment of phagocyte to microbe

Ingestion

• process of engulfing the microbe

Digestion

• uses digestive enzymes & strong oxidantes (H2O2)

  • Digestion & oxidation kills microbe

Inflammation definition

• defensive respond to tissue damage

  • This is an attempt to dispose of microbes, toxins, & foreign material at the site of injury to prevent the spread to other tissues, & to prepare the site for repair

Examples that cause inflammation

1. Pathogens

2. Abrasions

3. Chemical irritation

4. Cells disturbance

5. Extreme temperature

4 signs of inflammation

1. Redness

2. Pain

3. Heat

4. Swelling (edema) —> ice

Inflammation process

1. Injured cells release prostaglandins, proteins, & potassium ions

2. Mast cells release histamine (increases capillary permeability) & heparin (inhibits clotting)

3. Increases blood flow (raises local temp, causes area to swell, redden, & become painful)

4. Activated neutrophils attack debris & bacteria

5. Fibroblasts form scar tissue

Products of inflammation

1. Necrosis (local tissue destruction in area of injury)

2. Pus (mixture of debris & necrotic tissue)

3. Abscess (pus accumulated in an enclosed space)

4. Fever (abnormal high body temp that occurs because of hypothalamic thermostat reset)

   • Intensifies effects of interferons, inhibits some microbe growth, & speeds up reactions that aid in attack & repair

Pyrogens

• any material that causes the hypothalamus to raise body temperature including circulating pathogens, toxins, or antibody complexes

Immunity

• ability to mount a specific resistance against specific antigens

Immunity (specific)

• ability to signal out foreign substances for destruction, also recognizes self

Immunity (memory)

• to be able to remember an antigen & kill it faster next time

Immunity (systemic)

• affects the whole body (not restricted to the area of infection)

Antigens

• anything that is perceived as foreign due to surface proteins

  • Ex: viruses, bacteria, cancers, bacterial toxins, pollen, incompatible blood cells

3 common pathways to lymphatic tissue

1. Enter blood stream & are trapped as they flow through the spleen

2. Penetrate the skin, enter lymphatic and get lodged in lymph nodes

3. Penetrate mucous membranes & become entrapped by MALT

Antigen receptors

• before T cells leave the thymus & B cells leave red bone marrow, they insert specific proteins into the plasma membrane capable of recognizing specific antigens

T cells

• Kill other cells

B cells

• produce plasma cells that produce antibodies

Remember:

• all defenses go after the invader at once

  • Inflammation, fever, complement, neutrophils, macrophages, natural killer cells, T cells & B cells

Major Histocompatibility Complex (MHC)

• the body’s self antigens, a protein on the surface of all cells, how the body recognizes its own cells (except RBCs)

Class I MHC

• appear on all body cells EXCEPT RBCs

Class II MHC

• appear only on activated T cells & cells of the thymus

Cell-Mediated Immunity- Invasion By Antigen

1. Antigen is presented

   • Antigen gets noticed/discovered,, bumps into WBC, antigen presenting cell—> migrates to lymphatic tissue to present antigen to T cell

2. Activation of T cell

   • Antigen causes a small number of T cells to activate

3. Costimulation (interleukin 2)

   • Activation is complete after a second chemical confirmation (costimulation)

     • prevents unneeded immune responses

4. Proliferate

   • Makes copies of itself (divides) from a few to thousands

5. Differentiate

   • Forms different more specialized copies

6. Elimination

   • All T cells kill this way

Helper (CD4)

• recognizes MHC-II’s- secretes interludes 2 (provides more costimulant)

Cytotoxic (CD8)

• recognizes antigens combined w/ MHC I’s (body cells with: virus, tumor cell), cells gone bad

Perforin

• punches holes in the plasma membrane of target cell

Lymphotoxin

• activates enzymes in target cell that destroy cells DNA

Antibody-Mediated Immunity- Invasion of Antigen

1. Binding & activation of B cells

   • B cells can bind directly to antigen but are much more efficient when antigen is presented to B cellS

2. Costimulation

   • By T helper cell

3. Proliferate

   • B cells divide

4. Differentiate

   • Turn into memory & plasma cells

   • Plasma cells (living 4-5 days; provide hundreds to millions of antibodies)

   • Antibodies (antibodies bind with antigen)

5. Antibody action

Antibody structure

• 2 parallel pairs of polypeptide chains:

  • 1 pair of heavy chains & 1 pair of light chains

( each chain contains constant segment & variable segments)

Antibodies (immunoglobulins) - IgG

• most abundant (80%)

• Protects against bacteria, viruses, toxins, & triggers complement system, can cross placenta from M—>F (immunity to newborns)

Antibodies (immunoglobulins)- IgA

• 10-15%

• Found in secretions

  • Tears, mucus, saliva, breast milk

  • GI

    • Protects mucus membranes from bacteria & viruses

Antibodies (immunoglobulins)- IgM

• 5-10%

• First secretion of plasma cells, activates complement system, are antigen receptors on B cells

  • (anti-A & anti-B antibodies in blood plasma)

Antibodies (immunoglobulins)- IgD

• rare, act as a B cell antigen receptors, activation of B cells

Antibodies (immunoglobulins)- IgE

• rare, act as receptors on mast cells & basophils

• involved w/ allergic & hypersensitivity reactions

• help against parasitic worms

Neutralizing

• stops reactivity

Cross link clumping

• makes antigens stick together

Activating complement

• sequence of reactions that lead to:

  • Inflammation & increased phagocytosis