Cytosol proteins from normal lymphocytes, leukemic lymphocytes, and different cultured lymphoid cell lines were separated by two-dimensional mini gel electrophoresis. By staining with Coomassie blue, specific protein patterns were obtained. Very similar gel maps were produced by the cytosol proteins of chronic lymphocytic leukemia cells, hairy cells, and of in vitro grown B cells. Protein 36/6.2 (molecular weight/isoelectric point), consistently present in these cells, could not be demonstrated in normal lymphocytes. For the comparison of control Raji cells--an Epstein-Barr-Virus (EBV)-DNA carrying Burkitt's lymphoma cell line--with Raji cells induced for early antigen (EA) production, 35S-methionine-labelled total cell lysates were analyzed. In the induced cells, an additional protein (100/5.5) was found; this might be one of the immunologically defined EBV-associated antigens. These results demonstrate that two-dimensional mini gel electrophoresis can be useful for the characterization of leukemic cells in addition to the morphological, cytochemical, and surface marker analyses.

Immunosuppressive factor(s) in sera from patients with acute viral hepatitis B [serum inhibition factor(s) (SIF)] which functioned like an antiactivator of lymphocytes were further characterized and purified. The active moiety could be separated from immunoglobulins and other serum proteins by means of gel filtration, anion exchange, and affinity chromatography. The major SIF activity always copurified with albumin. Affinity chromatography with Cibacron blue agarose matrix followed by elution with 2 M NaCl proved an optimal procedure to obtain SIF-positive albumin fractions. The SIF moiety could be dissociated from albumin by use of 5 M NaCl or 6 M urea and was separated from protein by sequential molecular filtration and G-10 gel filtration indicating a low molecular weight substance. SIF activity of lower degree could also be detected in albumincontaining fractions derived from normal sera and exhibited similar biochemical properties as the factor which was isolated from patients' sera.The purified SIF fractions could not be stained with various protein dyes after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The active moiety was partially extractable with ch1oroform:methanol indicating a lipophilic nature. Common fatty acids or bile acids were excluded as causative factors by gas chromatographic-mass spectrometric and radioimmunologic analyses. These data suggest that the SIF effect is caused by an albumin-associated low molecular weight lipid or lipophilic peptide. SIF may be physiological immunoregulatory products of the immune system which are probably produced in response to a viral antigenic stimulus.Serum factors which suppress the mitogen-induced transformation of normal lymphocytes [serum immunosuppressive factors (SIFs)] have been frequently demonstrated in viral hepatitis (1)(2)(3)(4)(5) Brattlig, N. et al., unpublished observations; Grauer W., et al., unpublished observations). The term SIF will be used for the biological in uitro phenomenon of suppression of lymphocyte proliferation by serum which may be caused by different immunosuppressive substances. Biological studies indicated that SIF-positive sera contain antiactivators which interfere with the G1-phase of lymphocyte activation (6).The biochemical nature of these inhibitory factors was,