We spent a lot of time comparing B cell and T cell surface molecules and activation...

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Biology

We spent a lot of time comparing B cell and T cell surfacemolecules and activation â€“ how theyâ€™re similar and different. Foreach of the following, compare similarities and differences. Makesketches where indicated. Feel free to use additional sketches ifthey help you learn the material.
A. Compare the TH-Macrophage interaction (which activates THcells) with the TH-B cell interaction (which activates B cells).Make a sketch of each interaction that shows the important cellsurface proteins involved. Also state in words the sequence ofevents involved in each activation.
B. Compare T cell receptors (TCR) with B cell receptors (BCR).How do they form? What do they look like? To what do they bind?What is the difference between somatic recombination and classswitching (a.k.a. â€œisotype switchingâ€), and which of these happensonly for BCRs?
C. Compare antigen display on MHC-I with display on MHC-II.Where do displayed antigens come from? How do they get attached toMHC-I/II? What happens when the corresponding T cell binds to eachMHC? Which display is more important for your immune system torecognize viruses? To recognize bacteria?

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3.6 Ratings (552 Votes)

A The TH cells or Helper T cellsbecome activated when they are presented with peptide antigens byMHC class II molecules which are expressed on the surface ofantigenpresenting cells APCs Once activated they dividerapidly and secrete small proteins called cytokines that regulateor assist in the active immune responseAn antigenpresentingcell APC or accessorycell is a cell that displays antigen complexed with majorhistocompatibility complexes MHCs on their surfaces this processis known as antigen presentation T cells may recognize thesecomplexes using their T cell receptors TCRs These cells processantigens and present them to Tcells Almost all cell types canserve as some form of APC They are found in a variety of tissuetypes Professional antigenpresenting cells includingmacrophages B cells and dendritic cells present foreign antigensto helper T cells while other cell types can present antigensoriginating inside the cell to cytotoxic T cells In addition tothe MHC family of proteins antigen presentation relies on otherspecialized signaling molecules on the surfaces of both APCs and TcellsMacrophages phagocytose the externalagent pathogen and present it via the MHCClass II moleculesAfter their activation macrophages are able to express MHC classII and costimulatory molecules including the B7 complex and canpresent phagocytosed peptide fragments to helper T cellsBcells can internalize antigen thatbinds to their B cell receptor and present it to helper TcellsUnlike T cells B cells can recognize soluble antigen forwhich their B cell receptor is specific They can then process theantigen and present peptides using MHC class II molecules When a Thelper cell with See Answer

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