The presence of anti-H antibodies indicates which of the following?

• A. A previous infection with Coccidioides immitis
• B. A previous exposure to Histoplasma capsulatum
• C. An active infection with Cryptococcus neoformans
• D. An active infection with Histoplasma capsulatum

Answer: (D)

Anti-H antibodies are antibodies directed against a Histoplasma capsulatum antigen. Their presence means the immune system is actively responding to Histoplasma, which most aligns with an ongoing infection rather than a mere past exposure. In histoplasmosis serology, detecting specific antibodies typically accompanies active disease, especially when clinical symptoms are present and other tests support infection. While antibodies can persist after clearance, the existence of anti-H antibodies in the right clinical context points to active Histoplasma infection. The other fungi mentioned have different serologic targets and patterns, so anti-H antibodies don’t indicate those organisms.