The document summarizes key aspects of the lymphatic system and immunity. It describes the lymphatic system's role in returning excess fluid from tissues, transporting lipids, and helping immune defenses. It also outlines the two main types of immunity - innate and adaptive immunity. Innate immunity provides immediate, non-specific protection while adaptive immunity involves lymphocytes and memory cells that provide a slower but more specific response. The adaptive immune response includes both cell-mediated immunity involving T cells and antibody-mediated immunity involving B cells and antibodies.

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Chapter 17
The Lymphatic
System and Immunity

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Immunity
 Innate Immunity
 Fast, non-specific and no memory
 Barriers, pH extremes, Phagocytes & NK cells,
fever, inflammation, complement, interferon
 Adaptive Immunity
 Slower, specific & has a memory
 Lymphocytes: T-cells & B-cells

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Lymphatic System
 Lymphatic tissue
 Reticular connective tissue containing
lymphocytes
 Bone marrow
 Lymph- interstitial fluid in lymphatic vessels
 Returns excess filtration from capillaries- to
circulation
 Transport dietary lipids
 Maintenance & distribution- lymphoid organs
 Filter bacteria and help active defenses

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Lymphatic
System

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

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Lymphatic Vessels

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Lymphatic Vessels

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Lymphatic Flow
 From tissue to veins
 Pumped by muscle & respiratory pumps like
venous return

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Lymphatic Flow

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Lymphatic Flow
Interactions Animation
 Lymph Formation and Flow
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Lymphatic Organs
 Primary lymphatic organs- stem cells divide &
develop into mature B & T-cells
 Red bone marrow & thymus
 Secondary organs: immune responses occur
 Lymph nodes, spleen & lymphatic nodules

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Thymus
 Two lobed organ
 Posterior to sternum, medial to lungs &
superior to heart
 T-cells divide & mature
 Self reactive cells are removed

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Lymph Nodes
 Scattered throughout the body
 Concentrated near mammary glands, axilla &
groin
 Contain mature B-cells, T-cells dendritic cells
and macrophages
 Filter lymph, trap foreign substances
 Macrophages & lymphocytes destroy most foreign
substances

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Lymph Nodes

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Spleen
 Between stomach & diaphragm
 Contains blood filled venous sinuses and
RBCs, macrophages, lymphocytes plasma
cells & granular leukocytes
 destroys worn or defective blood cells &
platelets
 Stores platelets
 attacks foreign substances in blood
 Fetal hemopoiesis

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Innate Immunity: Barriers
 Skin: physical and chemical
 Epidermal structure & constant shedding
 Mucous membranes
 Sticky mucus layer straps microbes, etc. and cilia
move it out
 Fluids: tears, saliva, perspiration, nasal
secretions
 Dilute and antibacterial action
 Movement: flow of urine, defecation &
vomiting

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Internal Defenses: Proteins
 Interferons
 Interfere with viral reproduction in a cell
 Complement System
 Enhance other immune actions
 Break cell membranes
 Attract phagocytes
 Tag microbial cells for destruction
 Transferrins- bind iron and starve bacteria
 Antimicrobial peptides: lyse microbes

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Internal Defenses: Cells
 Phagocytes specialized to ingest microbes
and cellular debris
 Neutrophils
 Monocytes  macrophages
 5-10% of lymphocytes = Natural Killer (NK)
Cells
 Destroy microbes & tumor cells
 Present in lymph nodes & red bone marrow

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Inflammation
 Response to tissue damage
 Indicated by redness, pain, heat & swelling

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Inflammation
1. Damage  mast cells, basophils & platelets
release histamine
 increased permeability & vasodilation in
blood vessels
2. Leakage of clotting proteins into tissue-
 Isolate bacteria behind clot
3. Phagocytes attracted to site
 Neutrophils & macrophages eat & die
4. Pocket of dead cells = pus
 Moves to body surface or into cavity & is cleared

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Inflammation

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Fever
 Abnormally high body temperature
 New set-point of thermoregulation system
 Normal temperature control action with new set
point
 Stimulated by many toxins or internal signals
 Interleukin-1

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Adaptive Immunity
 Specifically directed against a particular type
of invader
 Involves cell or antibody directed against a
particular antigen
 Antigen can be any substance: microbe, food,
pollen, tissue
 Normally self–tolerant
 Does not attack normal body tissue

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Maturation of T and B cells
 From stem cells in red bone marrow
 B cells mature in bone marrow
 T cells migrate to thymus
 During maturation both make particular
proteins in plasma membranes = antigen
receptors

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Types of Responses
 Cell-mediated- T-cells attack directly
 Killer T-cells
 Antibody-mediated
 B cells become plasma cells
 Produce specific antibodies
 Helper T cells aid both cell- and antibody-
mediated responses

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Antigens & Antibodies
 Major Histocompatability Complex (MHC) = self
antigens on cells surface
 Unique to each individual
 Allows T-cells to recognize foreign material
 Antigen triggers plasma cell to produce antibodies
 Y-shaped protein with variable antigen binding site on
arms
 Other end triggers recognition by phagocyte

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Antigens & Antibodies

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Antigens & Antibodies

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Triggering Adaptive Response
 Requires recognizing the foreign antigen
 B-ceils can find it anywhere
 T-cells need presentation with MHC
 Antigen presenting cells (APC) do this
 APCs macrophages, dendritic cells & B cells
 In respiratory, GI, urinary, reproductive tracts
& lymph nodes

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Processing & Presenting Antigens
 APC’s ingest & digest into fragments in
vesicles
 Synthesize MHC & pack in vesicles
 Two vesicles fuse
 Antigen fragments bind to MHC
 Antigen-MHC complex inserted into plasma
membrane
 Presented to T-cells until a receptor matches
& binds

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Processing & Presenting Antigens

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Cell Mediated Immunity
 T-ceils also need costimulator
 Interleukin-2 (IL-2)
 Binding both  response
 T-cell begins rapidly dividing
 Forms a clone of many recognizing cells
 Helper T cells
 Release IL2, attract phagocytes, stimulate
macrophages & B cells

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Cell Mediated Immunity
 Cytotoxic T cells – kill cells
 Work against tumor cells transplanted cells &
infected cells
 Memory T cells- hang around for years, give
rapid response

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Cell Mediated
Immunity

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Cell Mediated
Immunity

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B-cells and Antibody-Mediated Response
 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

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Secretion of Antibodies

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Antibody Class Actions
 Neutralizing antigen
 Binds and neutralizes toxins
 Immobilizing bacteria
 Agglutinating
 Connect pathogens to one another  easier
phagocytosis
 Activating complement
 Enhancing phagocytosis
 Binding attracts phagocytes

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Immunological Memory
 Long lasting antibodies & lymphocytes
 Many sensitive memory cells 
 Much larger & quicker response next time =
Secondary Response
 Primary response can be naturally acquired
 Or artificially acquired by vaccination
 Killed cells, isolated antigens, parts of viruses

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Immunological Memory
Interactions Animation
 Introduction to Disease Resistance
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Aging
 Thymus atrophies
 Fewer responsive T cells
 Thus poorer B cell response
 Poorer response to new infection

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End of Chapter 17
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