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Which one of the following statements is true with regard to processing and presentation of protein antigens?
- a)In the class II MHC pathway, protein antigens in the cytosol are processed by proteasomes
- b)In the class I MHC pathway, extracellular protein antigens are endocytosed into vesicles and processed
- c)In the class I MHC pathway, transporter associated antigen processing (TAP) protein is required for translocating processed peptides generated in the cytosol
- d)Invariant chain in endoplasmic reticulum is involved in transport of peptides and loading of class I MHC
Correct answer is option 'C'. Can you explain this answer?
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Which one of the following statements is true with regard to processin...
Processing and Presentation of Protein Antigens
Introduction
Protein antigens play a crucial role in immune responses and are processed and presented by major histocompatibility complex (MHC) molecules. The MHC molecules are divided into two classes: class I and class II. The processing and presentation of protein antigens differ between these two classes.
Class I MHC Pathway
In the class I MHC pathway, intracellular proteins are processed and presented. This pathway involves the following steps:
1. Proteasomal Degradation: Intracellular proteins are broken down into smaller peptides by proteasomes, which are large protein complexes present in the cytosol. These peptides are typically 8-10 amino acids in length.
2. Transporter Associated with Antigen Processing (TAP): The processed peptides generated in the cytosol are then translocated into the endoplasmic reticulum (ER) by the TAP protein. TAP acts as a transporter, facilitating the movement of peptides from the cytosol to the ER lumen.
3. Peptide Loading: Once in the ER lumen, the peptides bind to the class I MHC molecules. This process is facilitated by chaperone proteins such as calnexin and calreticulin. The peptides are further trimmed by ER-resident aminopeptidases to achieve the optimal length for binding to class I MHC molecules.
4. Transport to the Cell Surface: The peptide-loaded class I MHC molecules are transported from the ER to the cell surface, where they are presented to CD8+ T cells.
Therefore, option C is correct: In the class I MHC pathway, transporter associated antigen processing (TAP) protein is required for translocating processed peptides generated in the cytosol.
Class II MHC Pathway
In contrast to the class I MHC pathway, the class II MHC pathway primarily involves the processing and presentation of extracellular proteins. The steps involved in this pathway are as follows:
1. Endocytosis: Extracellular proteins are endocytosed into vesicles called endosomes. This process allows the uptake of protein antigens from the extracellular environment.
2. Lysosomal Degradation: The protein antigens within the endosomes are degraded into smaller peptides by lysosomal enzymes.
3. Invariant Chain: In the ER, the invariant chain binds to the newly synthesized class II MHC molecules, preventing their premature binding to endogenous peptides. The invariant chain also assists in the transport of class II MHC molecules to the endosomes.
4. Exchange of Peptides: In the endosomes, the invariant chain is degraded, leaving a small fragment called the class II-associated invariant chain peptide (CLIP) bound to the class II MHC molecule. CLIP is then exchanged for the antigen-derived peptides within the endosomes.
5. Transport to the Cell Surface: The peptide-loaded class II MHC molecules are transported to the cell surface, where they are presented to CD4+ T cells.
Therefore, option B is incorrect: In the class II MHC pathway, extracellular protein antigens are endocytosed into vesicles and processed.
In conclusion, the correct statement with regard to the processing and presentation of protein antigens is option C: In the class I MHC pathway, transporter associated antigen processing (TAP) protein
Introduction
Protein antigens play a crucial role in immune responses and are processed and presented by major histocompatibility complex (MHC) molecules. The MHC molecules are divided into two classes: class I and class II. The processing and presentation of protein antigens differ between these two classes.
Class I MHC Pathway
In the class I MHC pathway, intracellular proteins are processed and presented. This pathway involves the following steps:
1. Proteasomal Degradation: Intracellular proteins are broken down into smaller peptides by proteasomes, which are large protein complexes present in the cytosol. These peptides are typically 8-10 amino acids in length.
2. Transporter Associated with Antigen Processing (TAP): The processed peptides generated in the cytosol are then translocated into the endoplasmic reticulum (ER) by the TAP protein. TAP acts as a transporter, facilitating the movement of peptides from the cytosol to the ER lumen.
3. Peptide Loading: Once in the ER lumen, the peptides bind to the class I MHC molecules. This process is facilitated by chaperone proteins such as calnexin and calreticulin. The peptides are further trimmed by ER-resident aminopeptidases to achieve the optimal length for binding to class I MHC molecules.
4. Transport to the Cell Surface: The peptide-loaded class I MHC molecules are transported from the ER to the cell surface, where they are presented to CD8+ T cells.
Therefore, option C is correct: In the class I MHC pathway, transporter associated antigen processing (TAP) protein is required for translocating processed peptides generated in the cytosol.
Class II MHC Pathway
In contrast to the class I MHC pathway, the class II MHC pathway primarily involves the processing and presentation of extracellular proteins. The steps involved in this pathway are as follows:
1. Endocytosis: Extracellular proteins are endocytosed into vesicles called endosomes. This process allows the uptake of protein antigens from the extracellular environment.
2. Lysosomal Degradation: The protein antigens within the endosomes are degraded into smaller peptides by lysosomal enzymes.
3. Invariant Chain: In the ER, the invariant chain binds to the newly synthesized class II MHC molecules, preventing their premature binding to endogenous peptides. The invariant chain also assists in the transport of class II MHC molecules to the endosomes.
4. Exchange of Peptides: In the endosomes, the invariant chain is degraded, leaving a small fragment called the class II-associated invariant chain peptide (CLIP) bound to the class II MHC molecule. CLIP is then exchanged for the antigen-derived peptides within the endosomes.
5. Transport to the Cell Surface: The peptide-loaded class II MHC molecules are transported to the cell surface, where they are presented to CD4+ T cells.
Therefore, option B is incorrect: In the class II MHC pathway, extracellular protein antigens are endocytosed into vesicles and processed.
In conclusion, the correct statement with regard to the processing and presentation of protein antigens is option C: In the class I MHC pathway, transporter associated antigen processing (TAP) protein
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Which one of the following statements is true with regard to processing and presentation of protein antigens?a)In the class II MHC pathway, protein antigens in the cytosol are processed by proteasomesb)In the class I MHC pathway, extracellular protein antigens are endocytosed into vesicles and processedc)In the class I MHC pathway, transporter associated antigen processing (TAP) protein is required for translocating processed peptides generated in the cytosold)Invariant chain in endoplasmic reticulum is involved in transport of peptides and loading of class I MHCCorrect answer is option 'C'. Can you explain this answer?
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Which one of the following statements is true with regard to processing and presentation of protein antigens?a)In the class II MHC pathway, protein antigens in the cytosol are processed by proteasomesb)In the class I MHC pathway, extracellular protein antigens are endocytosed into vesicles and processedc)In the class I MHC pathway, transporter associated antigen processing (TAP) protein is required for translocating processed peptides generated in the cytosold)Invariant chain in endoplasmic reticulum is involved in transport of peptides and loading of class I MHCCorrect answer is option 'C'. Can you explain this answer? for GATE 2024 is part of GATE preparation. The Question and answers have been prepared according to the GATE exam syllabus. Information about Which one of the following statements is true with regard to processing and presentation of protein antigens?a)In the class II MHC pathway, protein antigens in the cytosol are processed by proteasomesb)In the class I MHC pathway, extracellular protein antigens are endocytosed into vesicles and processedc)In the class I MHC pathway, transporter associated antigen processing (TAP) protein is required for translocating processed peptides generated in the cytosold)Invariant chain in endoplasmic reticulum is involved in transport of peptides and loading of class I MHCCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for GATE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Which one of the following statements is true with regard to processing and presentation of protein antigens?a)In the class II MHC pathway, protein antigens in the cytosol are processed by proteasomesb)In the class I MHC pathway, extracellular protein antigens are endocytosed into vesicles and processedc)In the class I MHC pathway, transporter associated antigen processing (TAP) protein is required for translocating processed peptides generated in the cytosold)Invariant chain in endoplasmic reticulum is involved in transport of peptides and loading of class I MHCCorrect answer is option 'C'. Can you explain this answer?.
Which one of the following statements is true with regard to processing and presentation of protein antigens?a)In the class II MHC pathway, protein antigens in the cytosol are processed by proteasomesb)In the class I MHC pathway, extracellular protein antigens are endocytosed into vesicles and processedc)In the class I MHC pathway, transporter associated antigen processing (TAP) protein is required for translocating processed peptides generated in the cytosold)Invariant chain in endoplasmic reticulum is involved in transport of peptides and loading of class I MHCCorrect answer is option 'C'. Can you explain this answer? for GATE 2024 is part of GATE preparation. The Question and answers have been prepared according to the GATE exam syllabus. Information about Which one of the following statements is true with regard to processing and presentation of protein antigens?a)In the class II MHC pathway, protein antigens in the cytosol are processed by proteasomesb)In the class I MHC pathway, extracellular protein antigens are endocytosed into vesicles and processedc)In the class I MHC pathway, transporter associated antigen processing (TAP) protein is required for translocating processed peptides generated in the cytosold)Invariant chain in endoplasmic reticulum is involved in transport of peptides and loading of class I MHCCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for GATE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Which one of the following statements is true with regard to processing and presentation of protein antigens?a)In the class II MHC pathway, protein antigens in the cytosol are processed by proteasomesb)In the class I MHC pathway, extracellular protein antigens are endocytosed into vesicles and processedc)In the class I MHC pathway, transporter associated antigen processing (TAP) protein is required for translocating processed peptides generated in the cytosold)Invariant chain in endoplasmic reticulum is involved in transport of peptides and loading of class I MHCCorrect answer is option 'C'. Can you explain this answer?.
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ample number of questions to practice Which one of the following statements is true with regard to processing and presentation of protein antigens?a)In the class II MHC pathway, protein antigens in the cytosol are processed by proteasomesb)In the class I MHC pathway, extracellular protein antigens are endocytosed into vesicles and processedc)In the class I MHC pathway, transporter associated antigen processing (TAP) protein is required for translocating processed peptides generated in the cytosold)Invariant chain in endoplasmic reticulum is involved in transport of peptides and loading of class I MHCCorrect answer is option 'C'. Can you explain this answer? tests, examples and also practice GATE tests.
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