Assertion: An organ transplant patient if not provided with 'cyclosporin A' may reject the transplanted organ.
Reason: Cyclosporin A inhibits activation of T-cells and interferes with destruction of non-self cells.

Both Assertion (A) and Reason (R) are correct and R is the correct explanation of A.

An organ transplant patient if not provided with 'cyclosporin A' may reject the transplanted organ because cyclosporin A inhibits T cell function, it caused immunosuppression and chances of rejection of transplanted organ are reduced. Thus, organ transplant patients are provided with cyclosporin A.