**Core Concept:** Hepatitis B infection, Hepatitis B surface antigen (HBsAg), Hepatitis B core antigen (HBcAg), and Hepatitis B e antigen (HBeAg).

In Hepatitis B infection, HBsAg is a viral surface protein found in the peripheral circulation and is indicative of acute or chronic infection. HBcAg, on the other hand, is a viral core antigen that is predominantly found within the nuclei of infected hepatocytes and not usually detected in the peripheral circulation. HBeAg is another antigen associated with active viral replication and is often found in the peripheral circulation during acute infection.

**Why the Correct Answer is Right:** HBcAg is the correct answer because it is the antigen predominantly found within the nuclei of infected hepatocytes and not usually detected in the peripheral circulation. This is in contrast to HBsAg, which is a viral surface antigen found in the peripheral circulation. HBeAg is also not the correct answer as it is associated with active viral replication and is commonly detected in the peripheral circulation during acute infection.

**Why Each Wrong Option is Incorrect:**

A. HBsAg: This option is incorrect because HBsAg is the viral surface antigen found in the peripheral circulation, not within the nuclei of infected hepatocytes.

B. HBeAg: This option is incorrect because HBeAg is associated with active viral replication and is commonly detected in the peripheral circulation during acute infection, not typically found within the nuclei of infected hepatocytes.

**Clinical Pearl:** Hepatitis B infection is caused by the Hepatitis B virus, which can lead to acute or chronic hepatitis. Understanding the distribution of antigens (HBsAg, HBeAg, and HBcAg) can help differentiate between acute and chronic infection and guide treatment decisions.