The correct option is C HLA
The genes related to kidney transplant rejection are present on p (shorter) and q (longer) arm of chromosome number 6. These genes are polymorphic with 6 pairs of alleles,namely, HLA-A, HLA-C, HLA-B, HLA-DP, HLA -DR and HLA-DQ. These genes present antigen which are identified as self and non-self by the immune system of the body and those cells or tissues that are identified as foreign by T-lymphocytes are subjected to destruction
So, the correct answer is 'HLA'