392 THIRD INTERNATIONAL LYMPHOKINE WORKSHOP

exposed to antigen (picrylated spleen cells). The Tact is Ly-l-2+, I-J+, Fc+ and does not appear after treatment with cyclophosphamide or adult thymectomy. Syngeneity in the I-J region between the source of the TsF and the picrylated cell used to trigger the release of nsINH is essential, but the genotype of the Tact is unimportant, i.e., the T suppressor factor conveys genetic restriction and presumably has binding sites for Tact, for the haptene, and for recognizing I-J. The factor has a molecular weight of 30-50,000 daltons and a pI of 6.3-6.6.

Purification and Characterization of a Lymphokine Produced by FcR-Stimulated B Cells. TOHRU MASUDA, TAKAYO SUZUKI, AND MUNEO MIYAMA-INABA, Department of Immunobiology, Institute for Immunology, Faculty of Medicine, Kyoto University, Kyoto, Japan.

FcRy-bearing B cells synthesize a lymphokine when the cells are stimulated with immune complexes. As has been reported (Cell. Immunol.. 39,238, 1978; 44, 51, 1919; Int. Arch. Allergy Appl. Immunol., 66,282, 1981; J. Immunol., Feb. 1982), the lymphokine, termed suppressive B-cell factor (SBF), inhibit the proliferation of precursor B cells, so that antibody production is suppressed in an antigen-nonspecific manner. This factor also suppress LPS responses of spleen cells, and the proliferation of B origin tumor cells in vitro, as well as in vivo. SBF has MW of 43K dalton and a H-2 gene product, perhaps coded by I-C gene. Therefore, there is a H-2 restriction between SBF and target cells to cause successful suppression. Recently, we established a hybridoma line by fusing FcRy+ B cells (BALB/c) stimulated with immune complexes with 3T3 cells. By using cells of this line, I would like to present in this paper (1) the biochemical nature of SBF; (2) the regulation mechanism of SBF, in comparison with the factor produced by FcRa-bearing B cells, and the in vivo significance of such factors released by FcR-bearing B cells.

OKT4+ T Lymphocytes Suppress Epstein-Barr Virus-Induced Activation of B Lymphocytes via Gamma Interferon. RONALD PALACIOS AND ULF ANDERSSON, Department of Immunobiology, Wallenberg Laboratory, Karolinska Institute, Lilla Frescati S-104 05, Stockholm, Sweden.

OKT4+ but not OKT8+ T lymphocytes from adults and neonates suppressed Epstein-Barr virus (EBV)-stimulated immunoglobulin (Ig) production of B lymphocytes from adults but not neonates. This suppressor activity was abrogated if antibodies against gamma interferon were added at the start of the cultures. Addition of gamma interferon at the beginning of the cultures efficiently prevented B lym- phocytes of adults but not of neonates from being activated to Ig production by EBV. From these results we suggest that OKT4+ T cells suppress EBV activation of B lymphocytes through gamma interferon and that cord blood B cells are not inhibited by OKT4+ T cells or gamma interferon due to their insensitivity to gamma interferon.

Radiochemical Purification of Hybridoma-Derived SIRS. T. M. AUNE, D. R. WEBB,* AND C. W. PIERCE, The Jewish Hospital of St. Louis, St. Louis, Missouri, and *Roche Institute of Molecular Biology, Nutley, New Jersey.

Soluble immune response suppressor (SIRS) is produced by concanavalin A-activated murine T lym- phocytes. After oxidation by macrophages in a H20rdependent process, SIRS suppresses immune re- sponses and inhibits cell proliferation by normal and neoplastic cells. A T-cell hybridoma producing SIRS constituitively was constructed to obtain sufficient material for purification and characterization; hybridoma-derived SIRS has been internally labeled with [‘Hlleucine. SIRS in supernatant fluids (- 10” cpm of nondialyzable radioactivity and -IO6 units of activity-reciprocal of dilution which suppresses responses 50%) was purified by a combination of molecular sieve chromatography and high- performance liquid chromatography on RP-18 and diphenyl columns. SIRS in 0.5 M HAc, 1 M pyridine buffer was eluted from the RP-18 column with 20% propanol and from the diphenyl column with 30% propanol. In the final purification step there was only one peak of radioactivity which comigrated with SIRS bioactivity. SDS-polyacrylamide gel electrophoresis of purified SIRS revealed a single radioactive band with an apparent molecular weight of 10,000 daltons. This purification procedure resulted in a 5000-fold enrichment of SIRS activity from culture supernatant fluids; purified SIRS contained about 50 units SIRS/cpm [sH]leucine. (Supported by NIH Grants RR-05491 and AI-15353.)