Q.42 Which statements about MHC molecules are correct?
- Class I MHC molecules are composed of two non-covalently associated glycoproteins, α and β chains.
- MHC genes are polymorphic.
- Class I MHC molecules are expressed on most nucleated cells.
- Class II MHC molecules are restricted to B-cells, macrophage and dendritic cells.
Choose the correct answer from the options given below:
- B, C and D only
- A, B and D only
- A, C and D only
- A, B and C only
MHC molecules are key to immune recognition, often tested in exams. This question evaluates four statements on their structure, genetics, and expression—crucial for T-cell activation.
Statement Breakdown
A: Class I MHC molecules are composed of two non-covalently associated glycoproteins, α and β chains.
False. Class I MHC has a heavy α-chain (glycoprotein, three domains) non-covalently linked to β2-microglobulin (β chain), but β2-microglobulin is not a glycoprotein—lacks carbohydrate chains.B: MHC genes are polymorphic.
True. MHC loci (HLA in humans) show extreme polymorphism with thousands of alleles, enabling diverse peptide presentation.C: Class I MHC molecules are expressed on most nucleated cells.
True. Found on nearly all nucleated cells to present intracellular antigens to CD8+ T cells.D: Class II MHC molecules are restricted to B-cells, macrophages and dendritic cells.
True. Primarily on antigen-presenting cells (APCs) like B cells, macrophages, dendritic cells for CD4+ T cell activation.Correct Answer: B, C and D Only
Option A, B and D only is wrong due to Statement A’s inaccuracy on glycoproteins. B, C, D align with immunology facts.
All Options Explained
Option Statements Correct? Reason A: B, C, D only Excludes A Yes A false (β2-microglobulin not glycoprotein); B, C, D true B: A, B, D only Includes A No A incorrect; skips true C C: A, C, D only Includes A No A false; skips true B D: A, B, C only Includes A No A false; skips true D Master MHC for exams—polymorphism aids pathogen evasion, expression patterns define immune roles.
