This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Transplantation, Subject name: Surgery
A 46 year-old man is on a waiting list to secure a renal transplant. The genetic locus of transplant antigens in humans is known as which? 
Select and explain. 
A. Rhesus (Rh), B. Ig (Immunoglobulin) A and IgM, C. Human leukocyte antigen (HLA), D. ABO
C: Human leukocyte antigen (HLA)
Answer: C: Human leukocyte antigen (HLA) 
Explanation: HLA was one of the first studied antigens.The transplant antigen is located on the surface. The strongest transplant antigen is known as the major histocampatibility complex (MHC) and is found in humans on chromosome 6. The higher the number of MHC matches, the better chance of survival for the allograft. However, zero MHC-matched grafts have been placed due to overwhelming demands. On the other hand, mismatch in ABO and Rh group results in hyperacute rejection are elevated .