**Core Concept**
The major histocompatibility complex (MHC) plays a crucial role in antigen presentation to T-cells, a process vital for initiating an immune response. MHC restriction ensures that only specific T-cells recognize and respond to antigens presented by MHC molecules on antigen-presenting cells (APCs).

**Why the Correct Answer is Right**
MHC restriction is a mechanism that prevents T-cells from recognizing and responding to self-antigens, thereby preventing autoimmune responses. APCs process and present antigens to T-cells through MHC class I and II molecules. MHC class I presents endogenously synthesized proteins to CD8+ T-cells, while MHC class II presents exogenously processed antigens to CD4+ T-cells. This restriction is essential for maintaining immune tolerance and preventing autoimmunity.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because MHC restriction does indeed regulate antigen presentation, but it is not the primary mechanism for restricting antigen presentation.
* **Option B:** This option is incorrect because MHC class I and II molecules are involved in antigen presentation, and MHC restriction ensures that T-cells recognize these antigens in the context of MHC molecules.
* **Option C:** This option is incorrect because costimulatory signals are crucial for T-cell activation, but MHC restriction is a separate mechanism that ensures T-cells recognize antigens presented by MHC molecules.

**Clinical Pearl / High-Yield Fact**
MHC restriction is a fundamental concept in immunology, and understanding its role in antigen presentation is essential for grasping the mechanisms of immune tolerance and autoimmunity. A key point to remember is that MHC class I presents endogenously synthesized proteins, while MHC class II presents exogenously processed antigens.

**Correct Answer:**