Lecture 17 Flashcards
(31 cards)
The soluble proteins that contribute to the innate immunity
can be divided into:
▪ Antimicrobial serum agents
▪ Proteins produced by cells
▪ Complement system: series of pro-enzymes
Antimicrobial Serum Agents
Lactoferrin
C-reactive protein (CRP)
Mannose Binding lectin
-Serum amyloid A protein
Lactoferrin
iron-binding protein that competes with
pathogens for iron, an essential metabolite
C-reactive protein (CRP)
Acute-phase protein that binds to
phosphocholine in bacteria membranes and function in
opsonization. It activates complement via the classic pathway
Mannose-binding lectin (MBL):
MBL recognizes carbohydrate
patterns, found on bacteria, viruses, protozoa, and fungi,
resulting in activation of the lectin pathway of the
complement system
Serum amyloid A protein (SAP)
binds to bacterial cell wall
lipopolysaccharide and serves as a receptor for phagocyte
attachment. Implicated in several chronic inflammatory
diseases, such as amyloidosis, atherosclerosis, and
rheumatoid arthritis
Interferon
▪ Small protein produced by certain white
blood cells and virally infected cells
▪ Produced in response to viruses, RNA,
immune products, and various antigens
Interferon alpha and Interferon
beta (Type I)
-Produced by any cell
act on neighboring uninfected cells
-inhibit transcription and translation
- Interferon gamma (Type II)
-Produced by: Th1, CTLs (CD8+), NK cells
▪ Promotes NK cell activity ▪ Increases activity of macrophages -increase expression of MHCI and MHCII -Promotes adhesion and binding required for leukocyte migration -antiviral effects -respond to cancerous growth
IFN-g: Granuloma
-▪ Body’s way of dealing with a substance it
cannot remove
IFNγ-induced granuloma formation:
1.activation of Th1 helper cells by
macrophages
2.as well as IL-1 and IL-2
3. The Th1 cells then surround the macrophages
4.Release of IFNy
5.repeat
6.macrophages surround the Th1 cells to wall of infection
What is the complement system important for
recruitment
of inflammatory cells and the killing or opsonization of
pathogens
What activates the complement system
activated by
cleavage (cascade reaction)
Three mechanisms of the complement system
Antibody-Antigen (classic pathway)
• Microbial or non microbial foreign substances
(alternative pathway)
• Mannose-binding lectin (MBL) (lectin pathway)
The Classical pathway
C1 binds to Ag-Ab complex ▪ Activated C1 cleaves C4 and C2 ▪ Formation of C3 convertase ▪ C3 is cleaved ▪ C5 is cleaved ▪ Sequential binding of C5b, C6-C9
Alternative Pathway
▪ Spontaneous cleavage of C3 based on multiple initiators ▪ Requires Factors B and D ▪ Formation of C3 convertase (less stable) • requires Properdin
MBL Pathway
Mannan-binding lectin (MBL), an acute phase protein found in serum binds to carbohydrate residues on cells or pathogen surfaces ▪ MBL-associated serine protease (MASP) binds to MBL ▪ This complex cleaves C4 and C2 much like activated C1 (classical pathway)
MAC
Three pathways converge with activation of C5 convertase ▪ C5b binds antigenic surface ▪ MAC is formed on surface ▪ C5Components: C5b,C6, C7, C8, C9 ▪ Poly-C9: perforinlike molecule
Functions of Complement-(C5b-C9)
• Cell lysis
Functions of complement -Opsonization
C3b, C4b, and C1q
Functions of Complement-Inflammation, anaphylactic reactions
C3a, C5a
Functions of complement -Clearance of Immune complexes
C3b
Function of complement -Viral neutralization
C3b, C5b-C9
Inhibitor of the classical pathway
C1 inhibitor