Drugs like cyclosporin A delay or inhibit rejection of graft post organ transplantation primarily by

The correct option is D inhibiting T-cell infiltration
Organ donation is the process of removing an organ from a live or dead individual surgically and placing it in another individual. The common organs that are transplanted are the heart, kidneys, liver or skin.

This procedure elicits an immune response in the body of the patient receiving the organ as it is a foreign tissue for the body and as a result immune cells start to attack it.

In order to prevent this, the immune system has to be surpressed such that it does not destroy the transplanted organ. Cyclosporin A, a chemical produced by the fungus Trichoderma polysporum, has the capability of suppressing the immune system by inhibiting the activation of T-cells and interferes with the destruction of non-self cells of the donated organ.

The action of cyclosporin A does not normally kill B-cells, macrophages or basophils.