## **Core Concept**
The question tests knowledge of fungal infections, specifically those that target reticuloendothelial cells. Reticuloendothelial cells are part of the immune system and are involved in the phagocytosis of foreign substances and cellular debris. The correct answer involves identifying a fungus known to infect these cells.

## **Why the Correct Answer is Right**
The correct answer, **C. Histoplasma capsulatum**, is right because it is a dimorphic fungus that primarily infects the reticuloendothelial cells. Upon inhalation of its spores, *Histoplasma capsulatum* can cause histoplasmosis, a disease that particularly affects the lungs but can disseminate to other parts of the body, including the reticuloendothelial system. This fungus is known to reside within the macrophages of the reticuloendothelial system, making it a classic example of a fungus that infects these cells.

## **Why Each Wrong Option is Incorrect**
- **Option A:** *Cryptococcus neoformans* primarily infects the lungs and the central nervous system, not specifically targeting reticuloendothelial cells. It is an encapsulated yeast that can cause cryptococcosis, particularly in immunocompromised individuals.
- **Option B:** *Coccidioides immitis* causes coccidioidomycosis, which primarily affects the lungs. While it can disseminate, it is not specifically known for infecting reticuloendothelial cells.
- **Option D:** *Blastomyces dermatitidis* causes blastomycosis, which can affect the lungs, skin, and other organs, but it is not particularly known for targeting reticuloendothelial cells.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that *Histoplasma capsulatum* is often associated with bird or bat droppings and can cause a range of disease from asymptomatic to severe disseminated infection, particularly in immunocompromised individuals. This fungus is a classic example of a pathogen that exploits the reticuloendothelial system.

## **Correct Answer: C. Histoplasma capsulatum**