1.04 UTF-8 0 0 0 Some antigens deliver a signal of great intensity using this system, so great that the B-cell does not require further signals from T helper cells to continue differentiation These antigens are few, but important 2 Thymus-independent (TI) antigens 1 these only cross-link many copies of the BCR, rather than additionally binding other surface receptors Generate B-1 cell responses to limit infection 2 TI-2 antigens 1 are repeated epitopes found often on microbial surface polymers 2 TI-2 antigens 1 bind the BCR (sIgM) as well as other receptors on the surface 2 TI-1 antigens 1 T-Dependent Antigen signals 2 1st Signal: Antigen –surface IgM 2nd signal = CD40-CD40L 3rd Signal = Cytokine binding to receptors 1 whay are in the light and dark areas of the GC 2 light: B-cells that become non-dividing centrocytes, moving nearer follicular dendritic cells Dark: B-cell progeny that move with T cells and become centroblasts in a developing germinal center in the B cell areas of the node Centroblasts are closely packed in the dark zone 1 Antigen is stabilized by _________ to promote B-cell activation and affinity maturation within iccosomes 2 FDC 1 How are antibodies delivered to tissues? 2 Across epithelial barriers, antibodies are actively transcytosed IgA dimers us the poly-Ig receptor, leaving the dimer stabilized by the secretory component 1 IgG uses the ___________________ for transport into extracellular spaces 2 Brambell Receptor 1 What are three examples of Cells expressing receptors for the Fc portion of antibody are stimulated by contact with antibody-coated microbes, enhancing memory responses 2 Phagocyte Mast cell NK cells 1 Complement does three things well what are they 2 Recruits and activates inflammatory cells Opsonizes microbes Chemically creates pores in the microbial surface 1 Complement has three pathways . What are they? 2 Lectin Pathway: recognizing mannose on the surface of a microbe Alternative Pathway: taking advantage of the microbial surface to perform a step Classical Pathway: recognizing bound Ig and initiating the cascade 1 recognizing mannose on the surface of a microbe 2 Lectin Pathway 1 taking advantage of the microbial surface to perform a step 2 alternative pathway 1 recognizing bound Ig and initiating the cascade 2 Classical Pathway 1 What are the three steps in the complement pathways? 2 Initiation step Amplification intermediate Effector functions (solid phase or diffusible) 1 Explain the Classical Pathway in detail. 2 More than two antibody monomer bind the surface of a microbe Activation of C1q to C1qrs C1qrs cleaves C4 into C4a and C4b C4b is bound covalently to the microbial surface C1qrs cleaves C2 into C2a and C2b C2b complexes with bound C4b to cleave C3 into C3a and C3b Amplification: lots of C3b on microbe surface Allows for alternative conversion of C3 Two forms of C3 convertase C3b or C4b are recognized by receptors on macrophages and neutrophils, opsonizing microbes while activating these phagocytes Terminal components further damage microbial membranes C5 is converted to C5b and C5a by either C3bBbC3b (alternative) or C4bC2aC3b (classical) convertases Deposition of C5b initiates pore formation by the membrane attack complex (MAC) 1 Diffusable components (C3a, C4a, and C5a) increase inflammation by degranulating mast cells (anaphylotoxins) does what? 2 Increase vascular permeability Promote fluid drainage to nearest node Promote adherence and chemotaxis Sets up increase innate and adaptive response 1