lymphatic capillaries --> lymphatic vessels --> thoracic duct --> left subclavian vein
---> right lymphatic duct --> right subclavian vein
Condition of too much tissue fluid called edema.
Pulmonary edema associated with congestive heart failure can be very dangerous
Elephantiasis caused by parasitic worm infection
Lymphoid organs
Red bone marrow is where all types of blood cells are produced,
including 5 types of white blood cells needed for immunity
red bone marrow in adults, skull, ribs, clavicle, pelvis, vertebrae
Thymus is located in upper thoracic cavity behind the sternum
T-lymphocytes mature here
Spleen is located in upper abdominal cavity just below diaphragm
Acts as a blood reservoir
Spleen nodules contain macrophages and lymphocytes help purify blood
Lymph nodes are 1 -25 mm protuberances along lymphatic vessels consisting of fibrous connective tissue.
Filled with nodules which contain macrophages and lymphocytes
Nodules can also exist outside of lymph nodes e.g. tonsils, adenoids, Peyer’s Patches
Lymph is purified at these sites.
Immunity can be specific or non-specific
Nonspecific defenses against infection
barriers such as skin, epithelia, mucous membranes
acid pH of stomach
Normal flora of gut, vagina pathogens from getting established
inflammation reaction
response to injury
pain, redness, swelling, heat
injured cells release bradykinin
induces mast cells to release histamine --> capillaries dilate (redness) and become more permeable (swelling)
temperature inhibits microbes, enhances phagocytosis WBC’s
Protective proteins, the "Complement System"
Amplify the inflammatory response
Permeabilize membranes invading microbes
Releases chemoattractants to phagocytotic cells
Specific defenses require two type of lymphocytes
Antigens are proteins, or CHO (e.g. glycoprotein) that body recognizes as non-self
B cells produced and mature in bone marrow
antibody producing cells
T cells produced in bone marrow and mature in thymus.
cells which either directly attack antigen bearing cells
or help regulate immune response
B cells directly recognize antigens and give rise to antibody secreting plasma cells
and memory B cells if stimulated to do so by "helper’ T cells
Process called "clonal expansion"
Memory B cells (which circulate in the blood) can redivide to plasma cells if antigen reappears at some later date
Different lymphocytes are produced for each antigen
"Antibody mediated Immunity"
a.k.a. Humoral immunity (since in bloodstream)
Different Types of Antibodies
| Antibody type | Location | Function |
| IgG | Main antibody in circulation Y-shaped |
Attacks bacteria, viruses, bacterial toxins, enhances phagocytosis |
| IgM | Largest antibody |
Activates complement cell clumping |
| IgA | Secretions like saliva and milk | Attacks bacteria, viruses, bacterial toxins, etc. |
| IgD | Membrane bound receptor | Don't know yet |
| IgE | Membrane bound receptor on basophils in blood and mast cells in tissue | Allergic response |
T-cells and "Cell Mediated Immunity"
T cells don't normally respond directly to antigens
APC or antigen presenting cells , typically macrophages, ingest the antigen bearing particle, antigens combine with MHC (Major Histocompatibility Complex) in APC plasma membrane.
Combination of antigen +MHC "presented" to helper T-cell
Cytotoxic T cells kill cells on contact secrete vesicles which contain perforin molecules which break down invading cell membranes.
Helper T cells stimulate other immune cells and produce lymphokines
Lymphokines stimulate more helper T-cells (positive feedback), macrophages to phagocytize, B-cells to differentiate into plasma cells.
HIV destroys helper T’s
Suppressor T cells suppress the immune response, can eventually shut down immune response
Memory T cells provide long lasting immunity.
When stimulated can release lymphokines & start things going again.
Induced Immunity
Active immunity can be acquired by individuals who are exposed to a disease who then will not be infected again by the same disease.
Memory B and T cells are responsible
They can react much more quickly and to lower doses of the antigen than ordinary B cells
Vaccines can provide long-lasting active immunity when administered to healthy people.
May be "attenuated" microbes (weakened bacteria or virus)
or closely related microbes that give only very mild cases of the target disease
Short-lived, "passive immunity"
Direct injection of antibodies to an ill person
Newborn babies acquire passive immunity from mothers
Breast feeding prolongs this.
Allergies
Allergies due to overactive immune system producing antibodies to otherwise benign substances not normally considered foreign
IgE is type of immunoglobulin found in the blood but also in cell membranes of "mast cells" found in most tissues
Mast cells start off life as basophils
Antigen’s, now "allergens" bind to IgE causing mast cells to release histamines
Histamines cause mucus secretion and air-way constriction
Basophils & other WBC’s may get in on the act
"Anaphylactic shock" sudden loss of blood pressure, often fatal.
"Allergy shots" work by inducing body to produce lots of IgG which out-competes the IgE antibodies located on mast cells
Cytotoxic T cells may attack transplanted organs -
Effect reduced if organs have same MHC’ s or if various immunosuppressive drugs are used
Autoimmune Diseases
Autoimmune diseases occur when antibodies and T cells attack the bodies own tissues.
e.g. Multiple sclerosis (MS), Systemic lupus erythmatosus (SLE), rheumatoid arthritis.