Lymphatic System/ Immune System
Orozco, Jaclyn Period 1
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Anatomy of the lymphatic system
Innate (natural) immune defenses
Humoral Response
Cellular Response
Antigens
Antibodies
Cells involved in the immune system
Disorders associated with the immune system
Adaptive (acquired) immune defenses
Uses the first or and second lines of defense to stop attacks by pathogens
First Line of Defense: Surface Barriers
Surface barriers are skin & mucous membranes along with their secretions
Physical barrier to most microorganisms
Keratin is resistant to work acids & bases, bacterial enzymes, and toxins
Mucosae provide similar mechanical barriers
Acid - acidity skin and some mucous secretions inhibits growth; called acid mantle
Enzymes - lysozyme of saliva, respiratory mucus, & lacrimal fluid kills many microorganisms; enzymes in stomach kill many microorganisms
Mucin - sticky mucus that lines digestive & respiratory tract traps microorganisms
First Line of Defense - external body membranes
Second Line of Defense: Cells & Chemicals
Second Line of Defense - antimicrobial proteins, phagocytes, & other cells
Many second line cells have pattern recognition receptors that recognize & bind tightly to structures on microbes, disarming them before they do harm
Phagocytes - white blood cells that ingest & digest foreign invaders
Neutrophils - most abundant phagocytes, but die fighting; become phagocytic on exposure to infectious material
Macrophages - develop from monocytes & are chief phagocytic, most robust phagocytic cell
Inflammation is triggered whenever body tissues are injured
Benefits of inflammation
Prevents spread of damaging agents
Disposes of cell debris & pathogens
Alerts adaptive immune system
Sets the stage for repair
Histamine is released by mast cells is key inflammatory chemical
Chemicals are released into ECF by injured tissues or immune cells
Third Line of Defense - attacks particular foreign substances
A specific defensive system that eliminates almost any pathogen or abnormal cell in body
It is specific - recognizes & targets specific antigens
It is systemic - not restricted to initial state
It has memory - mounts an even stronger attack to known antigens
Antigen -substances that can mobilize adaptive defenses & provoke an immune response
Targets of all adaptive immune responses
Most are large, complex molecules not normally found in body
Characteristics of antigens
Can be a complete antigen or hapten
Contain anti-gentic determinants
Can be a self antigen
Self Antigen - all cells are covered with variety of proteins located on surface that are not anti-gentic to self, but maybe antigenic to others in transfusions or grafts
Antibodies, produced by lymphocytes, circulate freely in body fluids
Bind temporary to target cell
Mark for destruction
Lymphocytes act against target cell
Directly by killing infected cells
Indirectly by releasing chemicals that enhance inflammatory response; or activating other lymphocytes or macrophages
B lymphocytes - humoral immunity
T lymphocytes - cellular immunity
CD4 cells usually become helper T cells that can activate B cells, other T cells, & macrophages; direct adaptive immune response
Some become regulatory T cells which moderate immune response
CD8 becomes cytotoxic T cells that are capable of destroying cells harboring foreign antigens
Autoimmune Disease - results when immune system loses ability to distinguish self from foreign
Autoimmunity - production of auto antibodies & sensitized TC cells that destroys body tissues
Hypersensitives - immune responses to percieved threat that cause tissue damage
Hodgkins Disease - is an acquired immunodeficiency that causes cancer of B cells, which depresses lymph node cells & leads to immunodefiecny
Human Immunodefiency - cripples immune system by interfering with activity of helper T cells
Immunodeficiencies - congential or acquired conditions that impair function or production
One set of important self proteins are group of glycoproteins called MHC proteins
Coded by genes of major histocompatibilty complex and unique to each individual
Contain groove that can hold price of self antigen or foreign antigen
T lymphocytes can recognize only antigens that are presented on MHC protiens
Antigen Presenting Cells
Do not respond to specific antigens
Play essential auxilliary roles in immunity
1. Dendritic Cells
Found in connective tissues and epidermis
Act as mobile sentinels of boundary tissues
Phagocytize pathogens that enter tissues then enter lymphatics to present antigens to T cells in lymph node
Most effective antigen presenter known
Key link between innate & adaptive immunity
2. Macrophages
Widely distinguished in connective tissues & lymphoid organs
Present antigens to T cells, which not only activates T cell, but also further activates macropahge
3. B Lymphocytes
Do not activate naive T cells
Present antigens to helper T cell to assist their own activation
Active Humoral Immunity
1. Naturally Acquired - formed in response to actual bacterial / viral infection
2. Artificially Acquired - formed in response to vaccine of dead / attenuated pathogens
Passive Humoral Immunity
1. Naturally Acquired - antibodies delivered to fetus via placenta / to infront
2. Articially Acquired - injection of serum; such as gramma globulin
Anitbodies aka immunoglobulins are protiens secreted by plasma cells
Capable of binding specifically with an antigen detected by b cells
Basic Antibody Structure
Overall T or Y shaped antibody monomer consists of 4 looping polypeptide chains linked by disulfide bonds
2 identical heavy chains
2 identical light chains
Variable regions at one end of each arm combine to form 2 identical antigen binding sites
Stems make up constant region
Classes
IgM
IgA
IgD
IgG
IgE
Antibody Targets & Functions
Antigens don´t destroy antigens; they inactive & tag them
Form antigen antibodies complexes
Defensive Mechanisms
Neutralization
Agglutination
Preciptation
Complement Fixation & Activation
Summary of antibody actions
Simplest, but one of most important defensive mechanism
Antobodies block specific sites on viruses or bacterial exotoxions
Prevent antigens from binding to receptors on tissue cells
Antigen antibody complexes undergo phagocytosis
Allows for antigen antibody complexes to become cross linked into large lattice like clumps
Soluble molecules are cross linked into complexes
Complexes precipitate out of solution
Precipated complexes are easier for phagocytes to engulf
Main antibody defense against cellular antigens
When several antibodies are bound close together on same antigen, complement binding sites on their stem regions are aligned
Antigen antibody complexes don´t destroy antigens; they prepare them for destruction by innate defenses
Antibodies go after extracellular pathogens; they don´t invade solid tissues unless lesion is present
Recent exception found; antibodies can act intracellularly if attached to virus before it enters cell
Activate mechanisms that destroy virus
The lymphatic system is a series of vessels and nodes that collect and filter excess tissue fluid (lymph), before returning it to the venous circulation. It forms a vital part of the body’s immune defense
Primary Lymphoid Organs
Thymus - stores immature lymphocytes and prepares them to become active T cells, which help destroy infected or cancerous cells
Red Bone Marrow - primary lymphoid organs that generate lymphocytes from immature hematopoietic progenitor cells. The bone marrow and thymus constitute the primary lymphoid tissues involved in the production and early selection of lymphocytes.
Second Lymphoid Organs
Lymph Nodes - The nodes filter out the damaged cells and cancer cells. These lymph nodes also produce and store lymphocytes and other immune system cells that attack and destroy bacteria and other harmful substances in the fluid
Tonsils - their location at the throat and palate, they can stop germs entering the body through the mouth or the nose. The tonsils also contain a lot of white blood cells, which are responsible for killing germs
Spleen - protect the body, clearing worn-out red blood cells and other foreign bodies from the bloodstream to help fight off infection
Peter´s Patches - they form an important part of the immune system by monitoring intestinal bacteria populations and preventing the growth of pathogenic bacteria in the intestines
Appendix - can destroy bacteria before it breaches the intestine wall during absorption