**Core Concept**
Peyer's patches are lymphoid follicles located in the ileum of the small intestine, playing a crucial role in mucosal immunity. They are involved in the sampling and processing of antigens from ingested food and pathogens, triggering a local immune response.

**Why the Correct Answer is Right**
IgA is the predominant immunoglobulin in mucosal surfaces, including Peyer's patches. It provides protection against pathogens in the gastrointestinal tract by forming a physical barrier and activating the complement system. In Peyer's patches, IgA is present as a dimer, linked by a J-chain, and is secreted into the intestinal lumen through the polymeric immunoglobulin receptor (pIgR).

**Why Each Wrong Option is Incorrect**
**Option A:** IgM is primarily found in the bloodstream and is involved in the early response to infections, but it is not typically associated with mucosal immunity.
**Option B:** IgE is responsible for triggering allergic reactions and is found in mast cells and basophils, but it is not characteristic of Peyer's patches.
**Option C:** IgG is the most abundant immunoglobulin in the bloodstream and provides long-term immunity against pathogens, but it is not predominantly found in mucosal surfaces like Peyer's patches.

**Clinical Pearl / High-Yield Fact**
Peyer's patches are an essential component of the gut-associated lymphoid tissue (GALT), which plays a vital role in maintaining mucosal immunity and preventing infections in the gastrointestinal tract.

**Correct Answer:** C. IgA.