This microphoto is from the lung of an HIV-positive patient with acquired immune deficiency syndrome. Macrophages contain numerous encysted bradyzoites of Toxoplasma gondii. See toxoplasmosis in the brain section of this website.
One of the many opportunistic infections afflicting immunosuppressed patients is that due to Toxoplasma gondii. Other organisms include CMV, C. albicans, P. carinii, C. neoformans, HSV, and H.capsulatum.
From the slide collection of the late Dr. Charles Kuhn