First line=external barriers
Second line=internal defenses (cells, chemicals)
First Line (external defenses)
Skin and mucous membranes
**Skin, keratin, mucous membranes
**Mucous secretion, acid secretion, lysosome secretion, cilia, etc.
Second Line (internal defenses)
**Macrophages, eosinophils, neutrophils, mast cells
**Mechanism of phagocytosis
***Opsonization (uses complement and antibodies)
*Large granular lymphocytes
Second Line (internal defenses) Cont.
*Inflammatory response (histamines)
**Redness, heat, pain, edema
**Vasodilation, vascular permeability
Second Line (internal defenses) Cont. 2
If inflammation is from a pathogen you get phagocyte mobilization
Second Line (internal defenses) Cont. 3
Second Line (internal defenses) Cont. 4
*Heat can "kill" things, increase reaction rates, make immune system work "better"
Third Line (adaptive defense)
Specific, systemic, creates memory
*Humoral (anti-body mediated immunity)
**Antibodies circulating in body fluids (humors)
*Cellular (cell mediated immunity)
**Direct or indirect attack
Substances that mobilize and provoke the immune system.
*Large, complex molecules not normally found in body
*Can be natural or synthetic
*Target of the immune response
2 functional properties
**Ability to stimulate proliferation of lymphocytes and antibodies
**The ability to react with the activated lymphocytes and antibodies
Called a Hapten
*Smaller molecule that must 'link' up with the body's own proteins
*The body now sees this as a foreign object and an immune response starts
*These proteins may be for normal body function, therefore this response may be harmful, not protective (hypersensitivities)
*Haptens have reactivity but not immunogenicity unless 'linked'
Some things that contain Haptens
common household and industrial products
Only a part of the antigen is immunogenic, this is the antigenic determinant
*Free antibodies or lymphocytes bind to these sites
*Can have a variety, especially in large complex molecules
**Why do plastics and metals make good implants compared to real tissue?
**Why is transplant surgery tough?
Antigens the immune system recognizes as "self" (usually!).
Think about the following:
How does my immune system know that if I am given a heart transplant that heart is not "me" ("self")? Isn't it all just heart tissue? What makes my heart tissue different from yours?
Proteins that are made by the Major Histocompatability Complex (a particular region of genes) of a cell.
*They are protein molecules that we 'recognize' as self but are antigenic to other individuals
*So much variation only identical twins have the same MHC proteins.
Two types of MHC proteins, Class I and Class II
MHC proteins can 'present' pieces of degraded antigens (Class II MHC proteins) or pieces of an antigen (abnormal protein) that the cell is actually producing (Class I)
*How do you degrade a non-self antigen?
*How do you make a non-self antigen?
**Think virus or other pathogens that take over the protein making processes of a cell.
Two types of MHC proteins Class I
Found on almost all body cells
Peptides 'displayed' to the immune system of these cells are made from normal protein breakdown. If the cell is infected (normal protein production gets screwed up), peptides of the foreign antigen will also be 'displayed'
Two types of MHC proteins Class II
Only found on cells involved in immune response (go ahead, name some!)
Only displays peptides from outside the cell
Cells of the Adaptive Immune System
B lymphocyte (B cell)
T lymphocytes (T cell)
Antigen-presenting cell (APC)
Lymphocytes Must Have
Immunocompetence - ability to recognize a foreign antigen
Self tolerance - unresponsiveness to self-antigen
Determination of Lymphocyte Type
Where a lymphocyte becomes immunocompetent determines if it becomes a T or B cell.
T for thymus, B for bone marrow (primary lymphoid organs)
T cell immunocompetence
Each cell must get a receptor that recognizes and binds to a specific antigen
*each T cell gets around 105 of only one receptor which is for a specific antigen
Must be able to bind to MHC (since this is where the antigens are presented to it)
Must not react too strongly to self-antigens in self
T cell immunocompetence 2
Step 1: Positive selection
*Occurs in cortex of thymus
*Creates T cells that recognize 'self-MHC'
T cell immunocompetence 3
Step 2:Negative selection
*Inner edge of thymus
*Tested to see if they react too vigorously to 'self'. If so, they are destroyed by apoptosis. We want cells that recognize 'self antigens' but we don't want ones that are so reactive that they may go 'haywire'.
**Only 2% of cells make it through this test!
B cell Immunocompetence
Not much known
*Those that react to self are destroyed, but some may be able to change their self reaction 'status' in bone marrow by 'messing' with the receptor site
B and T cells that are immunocompetent but have not been exposed to an antigen
*Exported to secondary lymph organs where antigen encounter occurs (the antigen challenge)
**Usually in spleen or lymph node
*After binding they differentiate into fully functional B and T cells
posed to antigen
Engulf an antigen and present a fragment of it to a T cell
*Dendritic cells (Langerhan's cells), macrophages, one function of an activated B cell
Humoral Immune Response
If the challenged cell is a B cell , humoral response evoked (antibody production)
*B cells rapidly multiply, some become plasma cells. These are the antibody secreters.
*This plasma cell process takes 5 days or so.
*Known as primary immune response
*Non-plasma cells become memory cells, which are long lived and can result in immediate reaction next time antigen is presented.
*Known as secondary immune response (faster, greater, stronger)
Cellular Immune Response Memory
Some T cells can become memory cells after a primary response activates T cells
Active and Passive Immunity
Active humoral immunity: what we have discussed so far. We can also give you the antigen artificially (vaccines, booster shots)
Passive humoral immunity: antibodies put into your system (crossing placenta, mom's milk, gamma globulins)
*Also called immunoglobulins (Ig), are the gamaglobulins of blood proteins.
Made up of 2 heavy chains and 2 light chains of looping polypeptides
*Identical for each class, except at a variable portion in each (pg 807)
*This creates the different classes
*Huge compared to other antibodies
*Constructed of five Y shaped units (monomers)
*Linked together to form a pentamer
*When in monomer form, is attached to B Cell surface and serves as an antigen receptor
*Pentamer circulates in blood plasma
*First Ig class released by plasma during primary response
*Indicates current infection
*Potent agglutinating agent due to numerous antigen binding sites
*Fixes and activates compement
*Occurs in monomer and dimer (two linked monomers) forms
*Exists in plasma in limited amounts
*Dimer referred to as secretory IgA
*Found in secretions such as saliva, sweat, intestinal juice, and milk
*Helps prevent attachment of pathogens to epthelial cell surfaces (mucous membranes & epidermis)
*Virtually always attached to external surface of a B cell
*Functions as an antigen receptor of the B cell
*Most abundant and diverse antibody in plasma (75-85%) of circulating antibodies
*Protects against bacteria, viruses, and toxins in blood and lymph
*Main antibody of both secondary and late primary responses
*Crosses the placenta and confers passive immunity to the fetus
*Slightly larger than the IgG antibody
*Secreted by plasma cells in skin, mucosae of the GI and respiratory tracts, and tonsils
*Stem binds to mast cells and basophils
*When receptor ends are triggered by antigen, cells release histamine and other chemicals that inflammation and allergic reaction
*Typically only traces found in plasma
*Levels rise during severe allergic attacks or chronic parasitic infections of the GI tract
Antibody functon (PLAN)
Binds to make an antigen-antibody complex
Makes antigens more 'presentable' to immune system cells by causing :
*Precipitation; causes it to "fall out"
*Lysis; complement fixation and activation
*Neutralization; blocking of antigen binding to normal cells
Specific for a single antigenic determinent
Can be made to attack only certain cells
Can be used to diagnose:
*Type 1 diabetes
*Severe combined ID syndromes
*Cancer of immune system cells (Hodgkin's)
Hypersensitivities (Type I)
Immediate or acute (Type I)
*Must be sensitized first. Antibody mediated
Hypersensitivities (Type II & III)
Sub acute (Type II and III)
*Antibody mediated. Slower and longer
Hypersensitivities (Type IV)
Delayed (Type IV)
**Allergic contact dermatitis