**Core Concept**
C3NeF is a autoantibody that stabilizes the C3 convertase enzyme complex, leading to uncontrolled activation of the complement system. This results in the consumption of C3 and the subsequent activation of the alternative pathway, causing a systemic inflammatory response.

**Why the Correct Answer is Right**
C3NeF is specifically associated with Dense Deposit Disease (DDD), a type of glomerulonephritis characterized by the deposition of dense material in the glomerular basement membrane. The autoantibody stabilizes the C3 convertase, preventing its normal inactivation and leading to continuous activation of the complement system. This results in the accumulation of complement components and the formation of dense deposits in the glomeruli.

**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect, as C3NeF is not associated with membranoproliferative glomerulonephritis (MPGN), which is characterized by the deposition of immune complexes in the glomeruli.
**Option B:** This is incorrect, as C3NeF is not associated with post-streptococcal glomerulonephritis (PSGN), which is caused by an immune response to streptococcal antigens.
**Option C:** This is incorrect, as C3NeF is not associated with lupus nephritis, which is caused by the deposition of immune complexes in the glomeruli due to systemic lupus erythematosus.

**Clinical Pearl / High-Yield Fact**
C3NeF is a specific marker for Dense Deposit Disease, and its detection is essential for diagnosing this condition. Remember that C3NeF stabilizes the C3 convertase, leading to uncontrolled activation of the complement system and the formation of dense deposits in the glomeruli.

**Correct Answer:** D. Dense Deposit Disease