1. Skin and Mucous Membranes

2. Lysozymes

3. Lactoferrin and Transferrin

4. Defensins

LYsozyme degrades peptidoglycan which is part of the bacterial cell wall

It is found in tears, mucus, milk, blood and ECF

They sequester iron, (depriving bacteria of it )

They are found in the same places as lysozymes (tears, mucus, blood, milk and ECF)

They ar short antimicrobial peptides that insert into bacterial/fungal membranes and form pores

They are found on mucous membranes and within phagocytic cells. 

It antagonizes the growth of pathogenic bacteria (competitive exclusion by taking up binding sites and nutrients)

It also provides constant stimulation of the immune system.

1. Tubule rearrangement in phagocyte to form pseudopodia.

2. Pseudopodia engulf foreign material=>phagosome

3. Phagosome fuses with lysozome=phagolysozome

4. Enzymes in lysozome break down foreign material

5. Digested material is either released from the cell or expressed on the surface. 

 They cause blood vessel dilation and leakiness

They attract phagocytes

1. Small blood vessels dilate

2. Leukocytes migrate out of bloodstream into damaged tissue

3. Clotting factors leak into damaged tissue

4. Tissue debris and dead neutrophils build-up (pus)

Increased blood flow

heat/redness

disruption of tight junctions between

endothelial cells-->leakiness

Prevents further bleeding

traps invading microbes in the clot

T/F

Complement proteins that circulate through the system are always activated.

False

Complement proteins circulate in an inactive form

1. Classical Pathway

2. Lectin Pathway

3. Alternate Pathway

Describe the cascade that occurs in the Classical Pathway

1. C1 is formed by the binding of C1q, C1r and C1s to an antibody-antigen complex on pathogen

2. C1 then cleaves both C2 and C4, forming C2a, C2b, C4a and C4b.

3. C2b and C4b go on to cleave C3 (forming C3 a and b)

4. C3b cleaves C5

1. Lectin protein binds to mannose residues, activating MASP-1 and MASP-2 (similar to C1 in classical)

2. MASP-1 and MASP-2 cleave C2 and C4

3. C2b and C4b cleave C3

4. C3b cleaves C5

1. C3b (from classical or lectin pathway) binds to a pathogen

2. Factor B binds to the pathogen bound C3b =>C3bB

3. Factor D splits Factor B in b and a, =>C3bBb

4.  Properdin binds=>C3bBbP

C3bBbP can split hundreds of C3 into C3a and b

C3a, C3b, C5a and C5b

The 'a's mediate inflammation

C3b opsonizes foreign material

C5b binds to C6 and C7 which then bind to the membrane of the foreign cell. C8 and C9 form the Membrane Attack Complex that forms holes in the membrane of the invader.

Infected cells stop producing MHC Class I molecules and so they cannot inhibit the killing signal for NK cells. 

NK cells then secrete perforin and granzymes which form holes and induce apoptosis while still preventing the release of viral particles from inside the cell.

An Antigen is any compound that can induce an antibody response. 

Proteins and polysaccharides are good antigens.

Lipids, nucleic acids and molecules with a MW that is less than 10 000 are poor antigens. 

T/F 

Each antigen has only one epitope

T/F

Each B cell can produce antibodies against a large diversity of antigens

False

Each B cell produces antibodies that are specific to only one type of antigen.

The heavy chains and the light chains.

The heavy chains form the inside of the Y, including the stem and the arms

The light chains for the outer limbs on the arms of the Y

1. The Fab fragment (arms) which binds antigen

2. The Fc part which interacts with other parts of the immune system

Name the 5 classes of antibodies

How can they be told apart?

IgM, IgA, IgD, IgG, IgE (MADGE)

They are identified by the amino acid sequence on their stem (Fc portion)

IgA

(A for abundant!)

IgE is bound to mast cells via its Fc region

 Two epitopes binding to IgE triggers degranulation

1. Gene Rearrangement

2. Imprecise joining of gene fragments

3. Hypermutation

T/F

Antibodies are found on the surfaces of naive B cells

CD8+ Cytotoxic T cells

CD4+ Helper T cells

MHC ( Major Histocompatibility Complex)

Class I presents cellular protein fragments

Class II presents exogenous antigens

How do T cells recognize antigens?

How do they respond?

Cytotoxic cells only recognize antigens when they are presented by MHC I.

They respond by producing cytotoxins like perforin and proteases (apoptosis)

Helper T cells recognize antigens presented by MHC II.

They then release cytokines that activate B cells, macrophages and cytotoxic T cells 

How can we use agglutination?

How does it work?

Agglutination refers to the clumping together of antigens when mixed with antibodies. 

Antigens only clump in response to their specific antibody so we can use this to determine blood groups and identify bacteria.

What do direct ELISAs test for?

Indirect ELISAs?

ELISA=Enzyme linked Immunosorbent assay

Direct tests for specific antigens

Indirect tests for specific antibodies

1. Attenuated-altered, living microbes that are not as virulent as the normal form but still produce immunity.

2. Inactivated-Dead microbes injected and their fragments create an immune response that is remembered.