This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'True about MHCAI- \nSelect and explain. \nA. Present on chromosome 4, B. Class III has complement, C. Class II comprises A, B, C loci, D. Class I is involved in mixed leucocyte reaction', 'role': 'user'}, {'content': 'Answer: B \nExplanation: MHC gene is present on the short arm of chromosome 6.\nClass II comprises DR, DQ, DP regions (A, B, C loci are present on class I).\nClass III consists of complement components,\nMixed leukocyte reaction involves class II MHC.\nThe histocompatibility antigens (human leukocyte antigens - HLA) are cell surface antigens that induce\xa0an immune response leading to the rejection of allografts.\nThe principal physiologic function\xa0of the cell surface histocompatibility molecules is to bind peptide\xa0fragments of\xa0foreign proteins for the presentation of antigen-specific T cells.\nThe histocompatibility antigens\xa0are encoded by a closely linked multiallelic\xa0cluster of genes -» Major\xa0histocompatibility\xa0complex (MHC) or Human leukocyte antigens\xa0complex (HLA complex).\nHLA complex of genes is located on the short arm of chromosome 6.', 'role': 'assistant'}]