An 8-year-old male is brought to his pediatrician's office by his mother. The child has had a runny nose, sore throat, cough, and low-grade fever for the past 24 hours. The patient's mother recalls that several of the child's friends have been ill recently with similar symptoms. The mother asks whether the child will need antibiotics for his condition. His pediatrician recommends symptomatic therapy and feels that his illness is most likely of viral etiology. Cytotoxic CD8+ lymphocytes are able to kill virus-infected nasal epithelial cells once sensitized. Cytotoxic CD8+ lymphocyte receptors recognize foreign proteins on the epithelial cell surface. Foreign proteins are presented on the epithelial cell surface by MHC molecules. These MHC molecules comprise which of the following components?

Question

An 8-year-old male is brought to his pediatrician's office by his mother.  The child has had a runny nose, sore throat, cough, and low-grade fever for the past 24 hours.  The patient's mother recalls that several of the child's friends have been ill recently with similar symptoms.  The mother asks whether the child will need antibiotics for his condition.  His pediatrician recommends symptomatic therapy and feels that his illness is most likely of viral etiology.  Cytotoxic CD8+ lymphocytes are able to kill virus-infected nasal epithelial cells once sensitized.  Cytotoxic CD8+ lymphocyte receptors recognize foreign proteins on the epithelial cell surface.  Foreign proteins are presented on the epithelial cell surface by MHC molecules.  These MHC molecules comprise which of the following components?

Quizplus · Accepted Answer

11ec160b_37b1_7278_9249_c52ee67a26a5_MD0001_00 Antigens are presented to cytotoxic CD8⁺ T-lymphocytes in association with MHC class I molecules. MHC class I is present on the surface of all nucleated cells. Each molecule of MHC class I protein consists of a single heavy chain and an associated β₂-microglobulin. Heavy chains are highly polymorphic, allowing them to present a large variety of antigens. After penetrating a cell, the virus uncoats and releases its core proteins. Some viral polypeptides are processed in the host cell cytoplasm and combined with MHC class I in the endoplasmic reticulum. The foreign antigen is then presented in association with MHC class I protein on the surface of the infected cell, signaling to CD8⁺ lymphocytes that the cell needs to be destroyed. The infected cell is ultimately eliminated via apoptosis. Important features of MHC class I and II molecules are compared below: 11ec160b_37b1_7279_9249_9d6bd97dde13_MD0001_00 (Choice D) MHC class II molecules consist of two polypeptide chains, alpha and beta. MHC class II molecules are present on the surface of antigen-presenting cells, including B-lymphocytes, macrophages, dendritic cells of the viscera, and Langerhans cells of the skin. Foreign antigens taken up by phagocytosis are degraded in lysosomes and presented to CD4⁺ T-helper cells in association with MHC II. Educational objective: CD8⁺ cells recognize foreign antigens presented with MHC class I proteins. Each MHC class I molecule consists of a heavy chain and a β₂-microglobulin. __________ References: Intracellular assembly and trafficking of MHC class I molecules. (http://www.ncbi.nlm.nih.gov/pubmed/19761542) MHC class I assembly: out and about. (http://www.ncbi.nlm.nih.gov/pubmed/18675588)

An 8-Year-Old Male Is Brought to His Pediatrician's Office by His