Immunocytochemistry of peripheral blood films from OHSt and healthy individuals. Blood films were stained with rabbit polyclonal antistomatin antibody (see “Patients, materials, and methods”) and counterstained with hematoxylin. Positive stomatin immunoreactivity is reflected by brown coloring. (A) Patient A-II-1. Some erythrocytes are stomatin immunoreactive (immunoreactive erythrocyte, IRE) but most are nonimmunoreactive (NIRE). All platelets (P) and the neutrophil (N) are immunoreactive. One lymphocyte is immunoreactive (immunoreactive lymphocyte, IRL), but the other is not (NIRL). (B) Patient B-II-1 shows a similar picture to patient A-II-1: mixed population of red cells; all platelets immunoreactive; and nonimmunoreactive lymphocyte. (C) Healthy control blood film. All erythrocytes are stomatin immunoreactive (IRE). All platelets are immunoreactive; there is a mixture of immunoreactive and nonimmunoreactive lymphocytes. (D-F) Negative controls, in which antistomatin antibody was omitted. (D) Patient A-II-1. Negative control and no first antibody. Neutrophil (N) and erythrocytes are all negative. (E) Patient B-II-1. Negative control omitting first antibody. (F) Normal blood film, negative control. Bar represents 10 μm.