Oligoclonal bands present on electrophoresis of concentrated CSF and concurrently tested in the serum may indicate which infection?

• A. multiple sclerosis
• B. HIV infection
• C. Guillain-Barre syndrome
• D. encephalitis

Answer: (B)

Oligoclonal bands reflect IgG that is produced in response to immune activity. When CSF shows oligoclonal bands and those same bands are also found in serum, it indicates that the IgG is coming from systemic circulation rather than being produced inside the central nervous system. In multiple sclerosis, the hallmark is oligoclonal CSF bands that do not appear in serum, showing intrathecal (within the CNS) IgG synthesis. When the pattern includes matching bands in both CSF and serum, a systemic infection or inflammatory state with broad IgG activation is more likely. HIV infection is known for polyclonal B-cell activation and increased IgG in both compartments, so seeing oligoclonal bands in CSF that mirror those in serum fits HIV infection. Guillain-Barre syndrome and encephalitis can alter CSF, but the specific finding of matching oligoclonal bands across CSF and serum is more characteristic of systemic immune activation such as HIV.