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midterm review - T cels

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Victor Barac

Antigens, Antibodies, & T-cell Receptor Structure II T-cell receptor : MHC contact – Transmembrane region  Contains lots of arginine and lysine  very unusual for hydrophobic transmembrane b/c they are +vely charged o Should disrupt ability to stay in membrane  But, exist for an important reason (to be discussed later) CD4 and CD8 cell surface proteins of T cells  Ig superfamily members – Bind to conserved region of MHC receptor to stabilize interaction   T cell can respond effectively to antigen  Passes signals that lead to T cell activation – CD4: 4 Ig domains; a monomer – CD8: 1 Ig domain; α + β form a heterodimer – Ensures right class of T cell associates w/ appropriate MHC receptor  Killer T cells  MHC class I = CD8 + +  Helper T cells  MHC class II = CD4 (recall: helper T cells activate B cells + humoral response) o Some exceptions – Cytoplasmic domain of CD4 and 8 pass signals to T cell  T cell receptor does interacting on outside   need CD8 + CD4 to pass signal into cell + to make sure binding is correct Immunoglobulin Structure and Function Isotype Differences – IgG [monomer]  cellular + humoral responses  Secreted by plasma cells, on surface of memory cells  Neutralize viruses and battles bacteria – IgE [monomer]  hypersensitivity  Seen only in allergic rxns – IgA [monomer in ECM, dimer secreted through epithelial surfaces]  mucosal immunity  Has J chain to bind dimer form – IgM [cell surface monomer, secreted pentamer]  B-cell receptor, humoral responses  Has J chain to bind petamer  1 secreted antibody you produce  On surface of naieve B cells Distribution of Antibodies – Blood plasma: IgG + petameric IgM – Below epithelial surfaces (respiratory, gut, skin): IgE  Why food allergies are common  skin rashes, hives, etc. – IgE is ready to react – Extracellular fluid: IgG + monomeric IgA – Secretions outside epithelia (milk, tears): dimeric IgA – Fetus: IgG  Can cross placental barrier  Material IgG passed to fetus to protect during pregnancy Synthesis of Immunoglobulins – Produced in the rough ER  pass through Golgi Transcytosis  cell surface  J chain synthesis istcoordinated – IgM always produced 1 in an immune response   low affinity, high avidity  each grip is loose, but there are lots (why pentomer works) – Isotype switching produces th
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