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Lymphocytes from normal adults, with or without serological signs of previous Epstein-Barr virus (EBV) infection, could be stimulated to proliferate and produce killer cells by incubation with autologous BBV-genome-positive lymphoid cell lines (LCLs). The stimulated cells were most probably of T-cell origin, although at the peak of stimulation many of them lacked the sheep erythrocyte marker. Direct effector-target cell contact was necessary for lysis to occur. The cytotoxicity of autologously stimulated (AS) lymphocytes was not restricted to EBV-genome-positive LCLs, nor to cell lines of hematopoietic origin. It was equally broad if cells carrying complement receptor had been removed before stimulation. Fresh lymphocytes, blasts induced by phytohemagglutinin or concanavalin A, and Burkitt's lymphoma biopsy cells were resistant or considerably less sensitive. Mouse cells—even cell lines—were resistant. The sensitivity of target cells to lysis correlated positively with their capacity to block AS lymphocyte lysis of autologous LCLs in competition experiments. The cytotoxicity of AS lymphocytes was blocked by EBV-genome-positive and -negative cell lines, whereas the EBV-related cytotoxicity of T cells from acute cases of infectious mononucleosis was blocked by EBV-genome-positive LCL only. [ABSTRACT FROM AUTHOR]

Human lymphoid cells isolated from the peripheral blood of adults, from cord blood, and from fetal liver, spleen, bone marrow, and thymus were cultivated with or without a cell-free preparation of Epstein-Barr virus (EBV) with demonstrated transforming activity. The cultures were examined for the EBV-associated nuclear antigen (EBNA) and for transfromation into permanent lymphoblastoid cell lines (LCL). EBNA, seen only in cultures that had received exogenous EBV, was detected between days 1 and 6 after addition of EBV, most frequently on day 3. EBNA-positive cells had a lymphoblastoid appearance. Transformation into established LCL became apparent between days 12 and 19. The addition of pokeweed mitogen to cultures containing EBV enhanced the development of EBNA, whereas phytohemagglutinin or concanavalin A had no such effect. Neither EBNA nor transfomration was observed in lymphoid cells from fetal thymus. In fetal spleen, bone marrow, and liver cells, EBV regularly induced EBNA and LCL transformation.

MLR histocompatibility typing was performed by in vitro stimulation of lymphocytes from various persons with fresh lymphocytes (irradiated) or with lymphoblostoid cell lines (mito-mycin-treated) derived from donors homozygous at the MLR locus. MLC responses to both types of stimulation correlated strongly suggesting that a) established lymphoblastoid line cells can express products of the MLR loc and b) fresh lymphocytes can be replaced by these long term lines in MLR typing. Two lines (LV-B and MS-B) derived from two MLR homozygous donors (lv and MS) were used throughout these experiments. It is possible that as additional lines are established from such MLR homozygous donors, a panel of typing cells could be created which would serve to standardize MLR typing and allow selection of unrelated but histocompatible donors for transplantation.

An Epstein-Barr virus (EBV)-negative lymphoblastoid cell line (LCL), BJA-B, was established from an African Burkitt's lymphoma (BL) which contained no detectable EBV DNA and did not express the EBV specified antigen EBNA, BJA-B cells grow in typically large, flat clumps. All carry surface-bound immunoglobulins, a B lymphocyte marker, and do not form rosettes with sheep erythrocytes. After infection of BJA-B cells by EBV the infected cells may produce either EBV-determined nuclear antigen (EBNA) or both EBNA and early antigen (EA), depending on the strain of EBV. The homogeneity of the BJA-B cell population with respect to immunological and isoenzyme markers and size suggests a clonal origin of the line. BJA-B is the first EBV-negative LCL established from an African Burkitt's lymphoma and demonstrates that an EBV-independent continuous B cell line can be established "in vitro" from other than leukemia or myeloma cells.

Three exceptional cell lines have been tested for the presence of the Epstein-Barr virus genome by nucleic acid hybridization (complementary RNA.DNA) and Epstein-Barr virus-determined nuclear antigen tests. Two lines were derived from Swedish lymphoma cases and one from an African Burkitt-like lymphoma biopsy that was negative for Epstein-Barr virus DNA and the virus-determined nuclear antigen. All three lines apparently lacked the viral genome. Two of the three lines clearly had characteristics of B-cells (bone-marrow-derived).

Epstein-Barr virus (EBV) derived from the B95-8 line has transforming activity for cord blood cells, whereas virus derived from the P3HR-1 line lacks such activity. When the two viral preparations were compared for their ability to infect the same EBV-genome-negative lymphoblastoid cell line, BJA-B, they induced approximately the same number of EBV-determined nuclear antigen (EBNA)-positive cells. EBNA is compatibile with continued cell proliferation. No early antigen (EA)-positive cells appeared in the B95-8 virus-infected cultures, whereas P3HR-1 virus-infected cells went on to express EA. EA signals the entry of the cell into the lytic cycle. No late viral antigen (VCA) appeared and, as a consequence, the P3HR-1 virus infection became abortive. In contrast, the EBNA-positive cells induced by the B95-8 virus continued to divide over several weeks. These findings show that different EBV isolates may differ in their biological activity, probably due to their having different degrees of viral dependence on restrictive host cell controls.