**Core Concept**
Henoch-Schonlein purpura (HSP) is a form of vasculitis characterized by the deposition of immune complexes in small blood vessels, leading to inflammation and leakage of blood into the skin and other organs. The condition is often associated with IgA antibodies.

**Why the Correct Answer is Right**
The correct answer is IgA deposits. In HSP, IgA antibodies are deposited in the walls of small blood vessels, including capillaries, venules, and arterioles. This deposition of IgA immune complexes triggers an inflammatory response, which leads to the characteristic purpuric rash and other symptoms of the disease. The IgA antibodies are often found in the affected vessels, particularly in the dermal papillae and around the vessels.

**Why Each Wrong Option is Incorrect**
* **Option A:** IgM deposits are not typically associated with Henoch-Schonlein purpura. While IgM antibodies can play a role in other forms of vasculitis, they are not the primary immune complex deposited in HSP.
* **Option B:** IgE deposits are more commonly associated with allergic reactions and conditions such as atopic dermatitis, rather than HSP.
* **Option C:** IgG deposits can be found in various forms of vasculitis, including systemic lupus erythematosus and polyarteritis nodosa, but they are not the characteristic immune complex deposited in HSP.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that Henoch-Schonlein purpura is a form of IgA vasculitis, and the diagnosis can often be confirmed by the presence of IgA deposits in the affected vessels. A high index of suspicion and knowledge of the characteristic clinical features and immunopathology are crucial for making an accurate diagnosis.

**Correct Answer:** C.