**Core Concept:**
Intravenous Immunoglobulin (IVIG) is a preparation of human immunoglobulins, which are proteins that play a crucial role in immune response. It is used to treat various autoimmune and immune-deficiency disorders. In the context of this question, IVIG is used for treating immune thrombocytopenic purpura (ITP), a condition where there is a decrease in platelet count due to excessive platelet destruction by the immune system. Steroids are often used to suppress the immune response in ITP patients.

**Why the Correct Answer is Right:**
Splenectomy is a surgical procedure performed to remove the spleen in patients with ITP, which is expected to increase platelet count by reducing platelet destruction. However, in this case, the patient is already on steroids, which are immunosuppressive and help in reducing platelet destruction. Despite steroids, the patient developed fever on the 3rd postoperative day, suggesting an increase in immune response. This increased immune response may lead to reactivation of a latent infection, known as post-splenectomy sepsis. In this scenario, IVIG is likely to be indicated because it suppresses the immune response and prevents the progression of post-splenectomy sepsis.

**Why Each Wrong Option is Incorrect:**
A. Steroids: While steroids are beneficial in ITP patients, their immunosuppressive effect might not be sufficient to prevent post-splenectomy sepsis in this case.
B. The fever could be due to surgical complications or an adverse reaction to anesthesia, not specifically related to the absence of the spleen.
C. Platelet transfusion: Transfusing platelets does not address the increased immune response that led to fever in this case.
D. Antibiotics: While antibiotics are essential post-operatively, they primarily address infection prevention rather than immune response modulation. The fever in this case is more likely due to an increased immune response following splenectomy.

**Clinical Pearl:**
IVIG is a valuable tool in modulating the immune response in ITP patients undergoing splenectomy, particularly when on immunosuppressive therapy. In post-splenectomy sepsis, IVIG can help prevent severe infections by suppressing the immune response.