<prompt> The role played by Major Histocompatibility Complex MHC-1 and -2 is to:AlIMS November 2014, November 2013Transduce the signal to T-cell following antigen recognitionMediate immunogenic class switchingPresent antigens for recognition by T-cell antigen receptorsEnhance secretion of cytokines  <response>: Ans. c. Present antigens for recognition by T-cell antigen receptors Ref: Harrison 19e p372e-1, 18e p497; Ananthanarayan 8e p132-135. 7e p129The role played by Major Histocompatibility Complex-1 and -2 is to present antigens for recognition by T cell antigen receptors. AIIMS November 2013 repeatMain function of MHC molecule is to bind peptide fragments of foreign protein for presentation to appropriate antigen specific T cells.Major Histocompatibility ComplexIn humans the gene encoding MHC or HLA complex are clustered on a small segment 4 megabase region of chromosome 6 short armQ 6p 21.3Q.HLA class I and class II genes whose products are critical for immunological specificity and transplantation histocompatibilityQ and they play a major role in susceptibility to a number of autoimmune diseases.Function: Binds peptide fragments of foreign protein for presentation to appropriate antigen specific T- CellsMHC is involved in Transplantation reactionQ Disease susceptibility autoimmuneQ, infectious and inflammatory disease Immune response and tolerance Complement component FeatureMHC-IMHC-IIMHC-lIIExpressed on presented byAll nucleated cells and plateletsQAntigen presenting cells including Dendritic cellsQ in lymph node and spleen, Langerhans cellsQ, Macrophages, B cellsQ and activated T cellsQClass III is present in between I and IIEncoded by component loci3 closely linked loci designated HLA-A, HLA-B and HLA-CHLA-D HLA DP, DQ, DRC4B, BF, C2 TNF a and bEncoding moleculeCell surface glycoprotein involved in antigen presentationQCell surface glycoprotein Involved in antigen presentationQComponents of complement systemQRecognized byCD8 T-cellsQ, NK cell recognitionCD4 helper T-cellsQ FunctionImmune response against intracellular infection, tumors, allograftsQGraft rejectionQCell mediated cytolysisQComponent of hormone receptorQGraft versus host responseQMixed leucocyte reaction MLRInfluence functional capacity of mature peripheral T cellsQ. 