<prompt> HLA-I is present on -All nucleated cellsOnly on cells of immune systemOnly on B-cellsOnly on T-cells  <response>: Ans. is a i.e., All nucleated cells o HLA-I - On surface of all nucleated cells and platelets,o HLA -II - Only on cells of immune system.o HLA complex consists of three separate clusters of genes :HLA Complex Class IClass IIClass IIIo Comprising A, B and C locio D region - DR, DQ, DPComplement region encodeso Responsible foro Responsible foro C2 C4 Graft rejection Graft versus host responseo Properdin factor B Cell mediated cytolysis Mixed leucocyte reactiono Heat shock proteino Found on the surface ofo Found only on cellso TNF -a and ball nucleated cells andof the immune system platelets 