The Lymphatic System & Immunity Chapter 17

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

Lymphatic System Lymphatic tissue – Bone marrow 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

Figure 17.1

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

Figure 17.2a

Figure 17.2b

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

Figure 17.3

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

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

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

Figure 17.4

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

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

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 & starve bacteria Antimicrobial peptides: lyse microbes

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

Inflammation Response to tissue damage Indicated by redness, pain, heat & swelling 1. damage mast cells, basophils & platelets release histamine  increased permeability & vasodilation in blood vessels

Inflammation (Cont.) 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

Figure 17.5

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

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)

Maturation of T & 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

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

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

Figure 17.6a

Figure 17.6b

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

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

Figure 17.7

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

Figure 17.8

Figure 17.9

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

Figure 17.11

Antibody Class Actions Neutralizing antigen- Binds & neutralizes toxins Immobilizing bacteria Agglutinating- Connect pathogens to one another easier phagocytosis Activating complement Enhancing phagocytosis Binding attracts phagocytes

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

Aging Thymus atrophies Fewer responsive T cells Thus poorer B cell response Poorer response to new infection