Agarose gel immunoblots, demonstrating the specific paraproteins responsible for immunoreactivity of patients 12 and 20 against HCMV. Patient 12, left; patient 20, right. Lane 1 depicts the serum protein electrophoresis (SPEP) pattern of major serum protein bands, as stained with amido black, without any protein transfer onto nitrocellulose. The image is that of the gel itself. The arrow and yellow dashed line denote the gel position of the serum paraprotein. The images for lanes 2 to 6 were scanned from a photographic film, after exposure to a nitrocellulose membrane. For lane 2, the membrane was probed for the presence of human IgG. For lanes 3 and 4, nitrocellulose membranes were precoated (prior to protein transfer) with inactivated, density-gradient purified HCMV whole virion (lane 3) or the antigenically unrelated M13 virus (lane 4). For lanes 5 and 6, nitrocellulose membranes were precoated with an HCMV lysate (lane 5) or a mock lysate derived from uninfected cells (lane 6). Each patient's image therefore represents a composite. For patient 12, the nonspecific band that is present in both the HCMV lysate lane (lane 5) and mock lysate lane (lane 6) does not comigrate with the paraprotein (lane 1, ).