**Core Concept**
Immunosuppressive agents are drugs used to prevent or treat the rejection of transplanted organs or tissues. They work by suppressing the immune system's ability to recognize and attack foreign substances, such as transplanted tissues or cancer cells.

**Why the Correct Answer is Right**
The correct answer is a drug that does not have immunosuppressive effects. The other options are known immunosuppressants used in various clinical settings to prevent organ rejection or treat autoimmune diseases.

**Why Each Wrong Option is Incorrect**
**Option A:** This drug is a calcineurin inhibitor, which works by inhibiting the production of interleukin-2 (IL-2) and other cytokines that stimulate T-cell proliferation. It is commonly used in organ transplantation to prevent rejection.
**Option B:** This drug is a corticosteroid, which has anti-inflammatory and immunosuppressive properties. It works by inhibiting the production of various cytokines and suppressing the activation of immune cells.
**Option C:** This drug is a monoclonal antibody that targets the CD20 receptor on B cells, leading to their depletion and reduced antibody production. It is used to treat autoimmune diseases such as rheumatoid arthritis and lupus.

**Clinical Pearl / High-Yield Fact**
The main difference between immunosuppressive and immunomodulatory drugs is their mechanism of action. Immunomodulatory drugs, such as cyclophosphamide, can modulate the immune response without completely suppressing it, making them useful in treating certain autoimmune diseases.

**Correct Answer:** D.