B Cells And Antibodies Flashcards
(43 cards)
What are B CELLS
Found in lymphatic system
Respond to antigens by differentiating into plasma cells and producing antibodies
How are they activated?
B cells receptors bind to specific antigens.
B cells in lymphatic tissue respond to unprocessed antigens or antigens presented by APC.
B CELLS respond to foreign things by taking some of it and combine it with MHC 2.
Complex recognised by helper T CELLS.
T cells make cytokines IL 2,4,6
THEY co stimulate b cells
After activation some of b cells enlarge and become different into the plasma
Plasma secretes antibodies specific to starting STIMULATING antigen
Some b cells don’t differentiate into plasma cells but turn into memory cells
What are antibodies?
Made up of 4 polypeptides chains
2 identical heavy chains: 450 amino acids and carb chains
2 light chains: 220 amino acids
What is each chain bound to by?
What are two chains held by?
Bound to heavy chain by disulfide bond
Two chains held by: disulfide bonds which make hinge region of antibody.
Heavy chains form a common stem region
What do both ligh and heavy chains have in common
V and C regions
V region?
Specificity of antibody
Found at tips of H and I chain at apex of antibody arms
Each antibody has two antigen binding sites.
Flexibility of hinge region lets the two recognition sites bind to widely separated antigens
Constant C region?
Same in different antibodies
Has H and L chain regions not associated to antigen binding
C region of H chain
Differs between different classes of antibodies
Allows classification of antibodies in 5 different classes
Eg: IgG IgA IgM IgD IgE
What is a COMPLEMENT
Complex system of a number of SERUM PROTEINS act in a sequence
Is the major effector mechanism in humoral defence against extracellular microorganisms
Name complement proteins and factors
C1 C2 C3 C4 C5 C6 C7 C8 C9
Factor B FACTOR D and Properdin
MBP: Mannose binding protein
Some are receptors on cells and in control of sequences
Name complement receptors?
CR1,2,3
Complement microorganisms
Innate Alternative pathway: C3 B D P
LECTIN INNATE PATHWAY: MBP C4, 2
Complement antigen or antibody (IgM, IgG) COMPLEXES
Specific pathway C1 C4 C2
What do they lead to
Terminal sequence C3,5,6,7,8,9
Create biological effects
How does the specific pathway work
Antibody IgM/IgG binds to epitopes of antigen
C1 binds to FC region of antibodies
C1r activates C1s which is a proteinase
C1s cleaves C4
C4b binds to antigen
C4a remains in fluid phase
C1s cleaves C2
C2 binds to antigen, C2 remains in fluid space
C2b binds to antigen, c2a stays in fluid space
C2b cleaves C5
C2b is a proteinase cleaves C3
C3b binds to antigen C3 in fluid space
C2b cleaves C5
C5 no spontaneous binding, c5a in fluid space
C5 binds C6,7,8 in fluid phase
C5b678 bind to lipid bi layer
C9 is a pore forming protein which inserts a whole into the membrane
What is the microorganism lysed by
Membrane attack complex
What is the membrane attack complex
Complement cascade is enzymatic
Each enzyme cleaves many molecules of substrate
Lots of MAC deposited into lipid bilayer membrane of cellular antigens
What does the MAC form?
Pores in the lipid bi layer membrane of microorganism’s
What does MAC KILL
G.E.P
Gram negative bacteria
Enveloped viruses
Protozoan parasites
What do GRAM POSITIVE BACTERIA PROTECT THEM SELF FROM
complement mediated lysis by their thick peptidoglycan cell walls
What do fungi protect themselves from
Complement mediated lysis C.M.L by thick chitin cell walls
Is there any cell lysis for gram-positive microorganisms?
At which cleavage does the pathway end?
No cell lysis
At C5
Other biological effects?
Complements have important role in elimination from body
From complement cleavages: C3A,5A, C3b
What are C3A and C5a?
What do they activate?
Anaphylatoxins and chemotaxis
Activate mast cells and attract phagocytes (NUETROPHILS and MONONUCLEAR phagocytes)
