Representative serum indirect immunofluorescence assay. Sera were tested in a 1:20 dilution by incubation on an HHV-8–containing cell line (KS-1); approximately 30% of the KS-1 cells express HHV-8 proteins, whereas the remainder act as internal controls. (A) represents a positive control, (B) a negative control, (C and D) two MM patients, (E) a breast cancer patient, and (F) an AIDS patient with KS. Positivity, green fluorescence restricted to approximately 30% of the cells is seen in the positive control and the AIDS patient only.