Cell Imm L1 ROUGH NOTES

Cell Imm Methods MCQ Material What is an antibody? Produced in response to non self by plasma B cells. Each plasma B cell identical antibodies bind to same epitope. Many plasma B cells activated by same immunogen produce different antibodies because different epitopes. B cell activation/Clonal selectionRequires antigen bind to BCR and co stimulation by CD40 (T cell dependent) or danger signalling (T cell independent) Results in clonal expansion and diff into plasma or memory cellsT cell dependent - T cell independent - CD40 on cell surface. Ag binds to BCR, ingested and processed, Ag presented on MHC II, BCR recycled, activates Th cell, gives co signal, memory and plasma cell increasePlasma or Memory CellPlasma - Ab factory (2000 Ab per second) short livedMemory - Produced mainly be T cell dep activation. Larger pop than naïve B cells, easier activated than B cells. Ab more specific than B cells - affinity maturation. Class switching done. Class Switching All B cells initially mainly IgM and some IgD. IgM = pentamer. Monomer = BCRAs B cells mature switch isotope controlled by cytokines. Each isotope different properties.Ab FunctionsDo not kill/remove pathogens aloneRecognise/bind Ag and trigger effector functionIsotope important, Fc region determines effector functionFunctions: opsonisation, complement activation, ADCC, agglutination, degranulationComplement FixationIgG (two IgG needed) and IgM neededFc regions activate complement cascade when Ag bound Disrupts pathogen membraneCan be opsonised for inc phagocytosisOpsonisation Promotes phagocytosis by neutrophils and macrophages Fc bind on phagocyte membrane Agglutination Ab bind two Ag (or more if multivalent i.e IgM)Pathogens bound together, prevent their normal functions, more efficient phagocytosisADCC - Antibody Dependent cell mediated cytotoxicity Ab bind to Ag, Fc region bound to effector cellDegranulation IgE only. Unusual, Fc primes effector cells before binding to Ag. Granulocytes release granules by cross linking Fc receptors on granulocyteIgM - good complement, opsoniser, agglutinatorIgA - Protects mucosal, resistant stomach acid, secreted in milkIgG - ok complement fixer, good opsoniser, induce ADCC, cross placentaIgE - Defend against parasites, induce degranulation, role in allergyFc ReceptorsCells different Fc receptors each cellBind to Ab Fc initiates Ab mediated effector functionEach isotope different Fc region,Fc receptors for polymeric immunoglobulins - imp for transporting IgA dimers and IgM multimers across epth membraneNeonatal Fc receptor transfer IgG across placentaAb usesRespond infection and diagnosisDiagnosis - specific, easily manipulated i.e tagging. I.e Fluorescent in flow cytometry. HRP in ELISA

How Ab MadeAnimals injected with Ag along with adjuvant. Animal sacrificed. Ab purified directly from serum - polyclonal. B cells taken manipulated produce lots Ab - monoclonalAdaptions for diagnosisConjugation - i.e fluorescence, biotin, enzyme. FITC - Fluorescein isothiocyanate. Flow cytometry. HRP - enzyme biological assays. Catalyses OPD to DAP in presence of H2O2 produce yellow-orange colour. Also acts on chemiluminescent subs produce light i.e luminol oxidised catalysed by HRP, decay aminopthalate dianion provides light emission.