**Core Concept**
Wire loop lesions are a histopathological hallmark of lupus nephritis, particularly in the context of diffuse proliferative glomerulonephritis (DPGN). These lesions are characterized by thickened capillary walls due to subepithelial deposits of immune complexes.

**Why the Correct Answer is Right**
Diffuse proliferative glomerulonephritis (DPGN) is the most severe form of lupus nephritis, accounting for approximately 60% of cases. Wire loop lesions are a distinctive feature of DPGN, resulting from the accumulation of immune complexes in the glomerular capillary walls. This process leads to the activation of complement system and subsequent inflammation, causing the characteristic wire loop appearance under light microscopy. The proliferative component of DPGN is reflected in the increased number of mesangial and endothelial cells, along with the infiltration of immune cells.

**Why Each Wrong Option is Incorrect**
* **Option A:** Mesangial proliferative glomerulonephritis (WHO class II) is characterized by mesangial cell proliferation and immune complex deposition, but it does not typically exhibit wire loop lesions.
* **Option B:** Focal proliferative glomerulonephritis (WHO class III) is less severe than DPGN and may not show the same degree of capillary wall thickening.
* **Option D:** Membranous glomerulonephritis (WHO class V) is characterized by thickening of the glomerular basement membrane, but it is not typically associated with wire loop lesions.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that wire loop lesions are a key feature of lupus nephritis, particularly in the context of DPGN. The presence of these lesions can help differentiate lupus nephritis from other forms of glomerulonephritis.

✓ Correct Answer: C. Diffuse proliferative glomerulonephritis (WHO class IV)