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CDR
- complementarity-determining regions
- CDR1, 2, 3
- aka hypervariable regions within Ig and TCR molecules
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4 main differences between TCR and Ig
- Valence & conformation: TCR is monovalent (2 chains), resembling the Fab fragment of an Ig; Ig is bivalent (4 chains)
- Antigen recognition: TCR responds to peptide fragments associated with MHC; Ig recognizes linear and conformational epitopes of carbs/nucleotides/lipids/proteins
- Secretion: TCR cannot be secreted
- Somatic hypermutation: occurs only in B cells
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MHC
- major histocompatibility complex
- displays peptides for recognition by TCRs on T cells
- Class 1: derived from cytoxolic proteins; recognized by CD8+ cells
- Class 2: limited to professional APCs, macrophages, and B cells; recognized by CD4+ cells
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4 requirements for immunogenicity
- foreignness
- high MW (<1kDa not immunogenic, >6kDa immunogenic)
- chemical complexity
- degradability and interaction w/ host MHC (antigen processing can reveal internal epitopes, unstable substrates won't bind to TCR/BCR)
- amount administered
- method of administration
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4 Immunization administration methods and their characteristics
- subcutaneous: strongest response b/c Langerhan cells are very potent APCs
- IV: goes to spleen
- oral-GI: local Ab response in GI lamina propria, but generally produces a systemic state of tolerance
- intranasal: allergic response
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