BIOL 460 1st Edition Lecture 8 Outline of Last Lecture I. Nucleotide BiosynthesisOutline of Current Lecture II.ComplementIII. FunctionsIV. NomenclatureCurrent LectureImmunology Lecture 9- Complement and its activation. Sheep RBC immunized mouse ------ alpha (SRBC) (anti serum sheep RBC)Alpha (SRBC) + SRBC ------------- EXPECT: agglutination OBSERVE : SRBC lysisEhrilch discovered that cellular cells Ag added to serum should show interaction of Ab Ag to form a lattice i.e. agglutination. But instead SRBC lysis seen. 50 degrees celcius 1 hr.Alpha (SRBC) ---------------------------- + SRBC ------ AGGLUTINATIONInference: Substance causing lyses is not present after heat treatment. 50 degrees celcius 1 hr. Alpha (SRBC) ------------------------- + normal mouse serum ----- + SRBC -- lysisThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Normal serum has substance such that when the anti serum is added to SRBC causes lyses.Learnt about the substance- can be heat de- activated.- exists in normal serum.- Triggered by Ag. Ab recognitionControl experiment:Normal serum + SRBC ---- NOTHINGA complement -where heat reacted anti serum with the serum causes lyses. SRBCInactive complement -------- active complement ----- lyse SRBCComplement- is about 20 proteins made by the liver.- similar system is found in invertebrates and plants.Functions:1. Cell lysis.2. Helps in opsonization via phagocytosis binding.3. Activation of inflammatory response by anaphylatoxins (C3a, C5a).4. Clearance of immuno- complexes from blood.Reaction kinetics of a cascade:A, A (Active) A (Active)B------------ B(Active)B(Active)C---------- C(Active) Same kinetics 1 sec convert 100 molecules in each C (Active) step. In 3 sec 100 x 100 x100 = 10^6 molecules.D---------- D (Active)Cascade- Major amplification.Simple reaction without cascade: A(Active)D---------- D(Active) In 3 secs only 300 D (Active) molecules.Complement Activation:1. Covalent Modifications – make or break covalent bonds.2. Conformational change of a protein.Nomenclature:Classical Pathway: C1----------- C9Lectin Pathway : Mannose binding LectinAlternate Pathway: B, D, PControl:Controls all pathways. C1 inhibitor, DAF, H, ILarge molecules split into small molecules.C3 - C3a + C3bLarger fragment has a large fragment b. Smaller fragment has smaller fragment a.C1 C1q, C1r, C1s (complements) C1q has elongated globular head and held by C1r, C1s.C1q (complement domain) interacts with CH2 domain of Ab.Ig G C1 needs more than 1 CH2 domain. C1 domain and Ab domain must be apart by 39-40 nm to enable C1 to see multiple domains.How many molecules on bacteria to form Ab that is 30-40 nm apart?1. 1000 Ig G molecules to meet criteria.2. Ig M complement activation is better due to pentameric nature. Even a single Ig M can activate a complement.3. Aggregated immunoglobins can activate complement.C1q binds to CH2 domain of an Ab causing a conformational change in C1s.C1s (active) - C2 --- C2a + C2bAlso, C1s (active) - C4 -- C4a +C4bC2A + C4b---- form complexC2a C4b (active): C3 convertase.Both C2aC4b (active) and C3bC5b have high affinity for biological membrane.Ag.Ab binding on cell surface and C1 convert C2 and C4 in serum and them complex to attach to membranes.C5b C6C7C8C9 but C9 polymerised.C5bC6C7C8 poly C9. This forms a 110 A hole punctured in the membrane and water and ions flows out causing cell lysis.Functions:C1- recognizes Ag.Ab complex.C3b – clearing of immuno complex.C3b, C4b – binds to phagocytes.C3a, C5a- anaphylatoxins, ChemoattractiveC3b, C5b- high affinity for membrane. After cleavage, chemoattract in phagocytosis.Complement part of Innate system and pre- formed before infection: just waiting for activation.End of the complement is death- to kill microbes or infected cells or rid of the complexes in the arteries so no