The Lymphatic System and Immunity Flashcards by Monica Anne Colina

the ability to ward off damage or disease through our defenses

Immunity

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2 General Types of Immunity

Innate Immunity
Adaptive Immunity

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• defenses that are present at birth
• Fast, non-specific and no memory
— Barriers, pH extremes, Phagocytes & NK cells, fever, inflammation, complement, interferon

Innate Immunity

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• Slower, specific & has a memory
• adapts or adjusts to handle a specific microbe.
— Lymphocytes: T-cells & B-cells

Adaptive Immunity

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• Lymphatic tissue
— Reticular connective tissue containing lymphocytes
• Bone marrow
• Lymph- interstitial fluid in lymphatic vessels

Lymphatic System

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Reticular connective tissue containing lymphocytes

Lymphatic tissue

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interstitial fluid in lymphatic vessels

Lymph

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Functions:
1. Drains excess interstitial fluid.
2. Transports dietary lipids. - lipid-soluble vitamins
(A, D, E, and K) absorbed by the GIT.
3. Carries out immune responses.

Lymphatic System

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n Begin at lymphatic capillaries
q Slightly larger than blood capillaries q Overlapping cells like one-way valve q Pressure will force fluid in
n Merge to form larger & larger vessels q Thin walled and more valves than veins
n Periodically have lymph nodes
q Lymphocytes in capsuled structure
n à thoracic duct à L subclavian vein q At junction with jugular
n à R. lymphatic duct à R. subclavian vein

Lymphatic Vessels

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• From tissue to veins
• Pumped by muscle & respiratory pumps like venous return

Lymphatic Flow

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Two Groups of Lymphatic Organ

• Primary lymphatic organs
• Secondary lymphatic organs

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site where stem cells divide & become immunocompetent.

Primary lymphatic organs

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Primary lymphatic organs

• develop into mature B & T-cells
• Red bone marrow
• Thymus

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site for most immune responses occur

Secondary lymphatic organs

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Secondary lymphatic organs

• Lymph nodes
• spleen
• lymphatic nodules (follicles)

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Two lobed organ (bilobed)

Thymus

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located in the mediastinum between the sternum and the aorta

Thymus

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• T-cells divide & mature
— Self reactive cells are removed

Thymus

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• Scattered throughout the body
— Concentrated near mammary glands, axilla &
groin

Lymph Nodes

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Contain mature B-cells, T-cells, dendritic cells and macrophages

Lymph Nodes

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• Function as a type of filter, trap foreign substances — macrophages destroy some foreign
substances by phagocytosis
— lymphocytes destroy others by immune responses.

Lymph Nodes

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• Metastasis - the spread of a disease from one part of the body to another.
• Cancer cells may travel in the blood or lymph and establish new tumors where they lodge.
• Cancerous lymph nodes feel enlarged, firm, nontender, and fixed to underlying structures.
• Lymph nodes that are enlarged due to an infection are softer, tender, and movable.

Metastasis through Lymphatic Vessels

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the spread of a disease from one part of the body to another.

Metastasis

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Between stomach & diaphragm

Spleen

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Contains blood filled venous sinuses and RBCs, macrophages, lymphocytes plasma cells & granular leukocytes

Spleen

Performs three functions related to blood cells: (1) removal by macrophages of ruptured, worn out, or defective blood cells and platelets; (2) storage of platelets, up to one-third of the body’s supply; and (3) production of blood cells (hemopoiesis) during fetal life.

Spleen

• organ most often damaged in cases of abdominal trauma. • crushing injury may result in a ruptured spleen, which causes significant hemorrhage and shock. • Splenectomy - removal of the spleen • The spleen’s absence also places the patient at higher risk for sepsis (a blood infection) due to loss of the filtering and phagocytic functions of the spleen.

Ruptured Spleen

sepsis

blood infection

removal of the spleen

Splenectomy

egg-shaped masses of lymphatic tissue that are not surrounded by a capsule.

Lymphatic Nodules

occur in multiple large aggregations in specific parts of the body.

Lymphatic Nodules

Includes tonsils in the pharyngeal region and the aggregated lymphatic follicles (Peyer’s patches) in the ileum of the small intestine

Lymphatic Nodules

Tonsils are strategically positioned to participate in immune responses against inhaled or ingested foreign substances.

Lymphatic Nodules

- physical and chemical — Epidermal structure & constant shedding

Skin

Sticky mucus layer straps microbes, etc. and cilia move it out

Mucous membranes

- tears, saliva, perspiration, nasal secretions — Dilute and antibacterial action

Fluids

flow of urine, defecation & vomiting

Movement

Four main types of antimicrobial substances

A. Interferons (alpha-, beta-, and gamma-IFN) B. Complement System C. Iron-binding proteins D. Antimicrobial peptides

Interfere with viral reproduction in a cell

Interferons

— Enhance other immune actions — Break cell membranes — Attract phagocytes — Tag microbial cells for destruction

Complement System

bind iron and starve bacteria

Iron-binding proteins

lyse microbes

Antimicrobial peptides

specialized to ingest microbes and cellular debris (phagocytosis)

Phagocytes

Two major types of phagocytes

• Neutrophils • Monocytes -> macrophages

Natural Killer (NK) Cells

5-10% of lymphocytes

Present in lymph nodes & red bone marrow

Natural Killer (NK)

Destroy microbes & tumor cells

Natural Killer

Perforin

cytolysis

Granzymes

apoptosis

nonspecific, defensive response of the body to tissue damage.

Inflammation

Conditions that may produce inflammation

pathogens, abrasions, chemical irritations, distortion or disturbances of cells, and extreme temperatures.

Four characteristic signs and symptoms of inflammation

redness, pain, heat, and swelling

Can also cause a ___________ in the injured area.

loss of function

prime symptom of inflammation.

Pain

mast cells, basophils & platelets release histamine -> increased permeability & vasodilation in blood vessels

Damage

Isolate bacteria behind clot

Leakage of clotting proteins into tissue

Neutrophils & macrophages eat & die

Phagocytes attracted to site (chemotaxis)

- pus — Moves to body surface or into cavity & is cleared

Pocket of dead cells

The three stages of inflammation

(1) vasodilation and increased permeability of blood vessels, (2) phagocyte emigration (3) tissue repair

• Abnormally high body temperature — occurs because the hypothalamic thermostat is reset q Normal temperature control action with new set point

Fever

• Stimulated by many toxins or internal signals — Interleukin-1-cytokine that plays a role in the regulation of immune and inflammatory responses to infections.

Fever

cytokine that plays a role in the regulation of immune and inflammatory responses to infections.

Interleukin-1

Elevated body temperature intensifies the effects of interferons, inhibits the growth of some microbes, and speeds up body reactions that aid repair.

Fever

(1) specificity for particular foreign molecules (antigens) (2) memory for most previously encountered antigens

Adaptive Immunity

for particular foreign molecules (antigens)

specificity

for most previously encountered antigens

memory

Antigen can be any substance:

microbe, food, pollen, tissue

Does not attack normal body tissue

Normally self–tolerant

From stem cells in red bone marrow

Maturation of T and B cells

mature in bone marrow

B cells

migrate to thymus

T cells

During maturation both make particular proteins in plasma membranes

antigen receptors (molecules capable of recognizing specific antigens)

Two Types of Responses

1. Cell-mediated 2. Antibody-mediated/Humoral Immunity

• cytotoxic T cells directly attack invading antigens — Killer T-cells

Cell-mediated

• B cells become plasma cells — Produce specific proteins called antibodies (Abs) or immunoglobulins (Igs)

Antibody-mediated/Humoral Immunity

Produce specific proteins

antibodies (Abs) or immunoglobulins (Igs)

Helper T cells aid both cell- and antibody-mediated responses

Antibody-mediated/Humoral Immunity

• self antigens on cells surface — Unique to each individual

Major Histocompatability Complex (MHC)

a rare inherited disorder in which both B cells and T cells are missing or inactive by

Severe Combined Immunodeficiency Disease

aka bubble boy disease

Severe Combined Immunodeficiency Disease

Control: — Bolstering nutrition, bone marrow transplant, enzymatic replacement therapy, and gene therapy

Severe Combined Immunodeficiency Disease

• Requires recognizing the foreign antigen • B-cells can find it anywhere • T-cells need presentation with MHC • Antigen presenting cells (APC) process and present exogenous antigens. • APCs macrophages, dendritic cells & B cells n • Location: respiratory, GI, urinary, reproductive tracts & lymph nodes

Triggering Adaptive Response

• Ingestion of the antigen by APC • Digestion of antigen into peptide fragments - protein-digesting enzymes split large antigens into short peptide fragments. • Synthesis of MHC-II molecules. • Packaging of MHC-II molecules into vesicles. • Fusion of vesicles -peptide fragments and MHC-II molecules merge and fuse. • Binding of peptide fragments to MHC-II molecules. • Insertion of antigen–MHC-II complexes into the plasma membrane - combined vesicle that contains antigen–MHC-II complexes undergoes exocytosis.

Processing & Presenting Antigens

protein-digesting enzymes split large antigens into short peptide fragments.

Digestion of antigen into peptide fragments

peptide fragments and MHC-II molecules merge and fuse.

Fusion of vesicles

MHC-II complexes into the plasma membrane - combined vesicle that contains antigen–MHC-II complexes undergoes exocytosis.

Insertion of antigen

Interleukin-2 (IL-2)

T-cells also need costimulator

Release IL2, attract phagocytes, stimulate macrophages & B cells

Helper T cells (CD4 Tcells)

• kill cells — Work against tumor cells transplanted cells & infected cells

Cytotoxic T cells

hang around for years, give rapid response if the same antigen enters the body again in the future

Memory T cells

• Hang out in lymph nodes • Respond to antigen (faster if presented) • With IL-2 enlarge, divide and become a clone of plasma cells • Plasma cells produce & release antibodies that bind the antigen • Some remain as Memory B Cells — Ready to respond quickly if antigen met again

B-cells and Antibody-Mediated Response

Example of Immunological memory provides the basis for immunization by vaccination against certain diseases

polio

When you receive the vaccine, which may contain __________(weakened) or killed whole microbes or portions of microbes, your B cells and T cells are activated.

attenuated

Antibody Class Actions

• Neutralizing antigen • Immobilizing bacteria • Agglutinating • Activating complement • Enhancing phagocytosis

Binds and neutralizes toxins

Neutralizing antigen

Connect pathogens to one anotheràeasier phagocytosis

Agglutinating

Binding attracts phagocytes

Enhancing phagocytosis

• Long lasting antibodies & lymphocytes • Many sensitive memory cells à • Much larger & quicker response next time = Secondary Response • Primary response can be naturally acquired n Or artificially acquired by vaccination — Killed cells, isolated antigens, parts of viruses

Immunological Memory

deals with communication pathways that link the nervous, endocrine, and immune systems.

psychoneuroimmunology (PNI)

a hormone secreted by the adrenal cortex in association with the stress response, inhibits immune system activity.

cortisol

• psychoneuroimmunology (PNI) deals with communication pathways that link the nervous, endocrine, and immune systems. • cortisol, a hormone secreted by the adrenal cortex in association with the stress response, inhibits immune system activity. • under stress, people are less likely to eat well or exercise regularly, two habits that enhance immunity. • to increase stress resistance, cultivate an optimistic outlook, get involved in your work, and build good relationships with others. • adequate sleep and relaxation

STRESS AND IMMUNITY

• tend to produce more autoantibodies • Thymus atrophies = decreased production of thymic hormones • Fewer responsive T cells • Thus poorer B cell response • Poorer response to new infection

Aging

decreased production of thymic hormones

Thymus atrophies