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Biomedical subjects

S Ben-Efraim

Publications and source records attributed to S Ben-Efraim.

At least 91 records · Page 5Linked to original sources
PubMed1979

Type C virus and immunoglobulin A production by murine myeloma MOPC-315: two independent activities.

The suspected correlation between cessation of type C virus production and halt in immunoglobulin secretion by murine myeloma cells was studied. Employing two variants of the murine myeloma MOPC-315, immunoglobulin A-producing and nonproducing cells, we demonstrated that the two myelomas release similar levels of type C viruses which share common nucleotide sequences and that the viral genomes are equally expressed within the cells. Thus, the suggested relation between these two activities does not apply for MOPC-315 cells and probably for other murine myelomas also.

Animals↗
PubMed1979

Effect of the MER tubercle bacillus fraction on the responsiveness of mice to T-independent antigens.

The effect of treatment with the methanol extraction residue (MER) mycobacterial fraction on the immunological responsiveness of BALB/c mice to the T-independent antigens pneumococcal polysaccharide type III (SIIII) and trinitrophenyl-lipopolysaccharide conjugate (TNP-LPS) was ascertained. Pretreatment with MER prevented the establishment of immunological paralysis by threshold doses (10 or 15 microgram) of SIII and by a paralyzing dose of 100 microgram TNP-LPS. The induction of immunological paralysis by SIII was unaffected by treatment with the bacterial adjuvant Corynebacterium parvum and with the B cell mitogens PPD, LPS (Escherichia coli lipopolysaccharide), and dextran sulfate.

Animals↗
PubMed1979

Inhibition of mixed-lymphocyte reaction by quinine and lack of effect on plaque-forming cells and lymphoid-derived tumor cells.

Using Balb/c cells as responder cells and mitomycin-treated C57B1 cells as stimulator cells, it was found that quinine was inhibitory in a one-way mixed-lymphocyte reaction. Incorporation of [3H]-TdR was brought down to base levels in the presence of quinine. Quinine was not toxic for antibody-forming cells, and had no effect on plaque-forming cells formed by antibody-committed cells. The degree of [3H]-TdR incorporation of MOPC-315 tumor cells and Burkitt's lymphoma cells was not affected by the presence of quinine in the medium. The cytotoxicity of quinine for mitogen-stimulated cells was demonstrated in soft-agar cultures.

Animals↗
PubMed1978

Selective killing of mitogen-induced transformed cells by quinine sulfate in vitro.

Increase in incorporation of 3H-thymidine ([3H-]-Tdr) in blast-transformed cells was induced in vitro by either lipopolysaccharide or concanavalin A (Con A) in spleen cells of Balb/c mice and by Con A in rabbit peripheral lymphocytes. Small lymphocytes were not affected by the addition of quinine to the medium. This was shown by a dye exclusion test and by mitogen stimulation after exposure and removal of quinine from the medium. On the other hand, immunoblasts were not formed in lymphocyte cultures containing both quinine and the cell mitogen. The degree of [3H]-Tdr incorporation after mitogenic stimulation was also markedly reduced by subsequent addition of quinine. An incubation period of at least 5 h was required for the expression of quinine effect. It is concluded that quinine acts as a cytotoxic agent for immunoblasts in vitro.

Animals↗
PubMed1976

An improved quantitative plaque assay for lymphocytes bearing antigen-specific cell receptors.

An improved method for the determination of the number of lymphoid cells bearing antigen-specific receptors is described. The method is based on the use of hapten-coupled bacteriophage (dinitrophenyl-T4) and detection of lytic plaques formed by the action of DNP-T4 on a target E. coli strain. The method is highly specific (up to 90% specific binding) and can be adapted for use with other antigenic determinants chemically attached to an active bacteriophage.

Animals↗
PubMed1976

Differences between lymphoid cell populations of guinea pigs and mice as determined by the response to mitogens in vitro.

The stimulation of guinea pig lymphocytes by phytohemagglutinin (PHA), concanavalin A (ConA), methanol-extracted residues of tubercle bacilli (MER), purified protein derivative of tubercle bacilli (PPD), dextran sulphate (DS) and E. coli lipopolysaccharide (LPS), was determined and compared with that of mouse lymphoid cells. The sources of lymphocytes tested were spleen, thymus, lymph nodes and bone marrow. The degree of activation of DNA synthesis by PHA and ConA was higher in guinea pig thymocytes and lymph node cells than in corresponding sources of mouse lymphocytes. The optimum degree of stimulation by PHA and ConA was approximately the same in guinea pig thymocytes, while ConA was by far a better stimulator than PHA for mouse thymocytes. All four B-cell mitogens tested (MER, DS, PPD and LPS) activated DNA synthesis in mouse lymphoid cells while only MER and DS were effective in guinea pig lymphocytes. A guinea pig spleen cell population depleted from B cells was not stimulated, neither by DS nor by MER, while it still responded to PHA and ConA. These results indicate that the proliferative response due to MER and DS occurs in the B-cell compartment. It is suggested that the differences between guinea pigs and mice with respect to their ability to develop a cell-mediated type immunity and to respond to T-independent antigens are related to differences in the relative proportions and degrees of maturation of T- and B-cell subpopulations, as reflected by the selective responsiveness to various mitogens.

Animals↗
PubMed1975

Mitogenic and adjuvant activity of a methanol extraction residue (MER) of tubercle bacilli on mouse lymphoid cells in vitro.

The mitogenic and adjuvant effect in vitro of MER (methanol extracted residue of tubercle bacilli), on Balb/C and nu/nu immunocompetent cells was examined and compared with the effect of PPD, LPS, DS, PHA and ConA. MER activated DNA synthesis in spleen cells of Balb/C and nu/nu mice and in blood cultures of Balb/C. The stimulation of DNA synthesis by MER in spleen cells was not macrophage dependent. Bone marrow and 1ymph node cells were slightly stimulated while thymus cells were not affected. Both MER and PPD enhanced the in vitro immune response of Balb/C mice to SRBC and to TNP (trinitrophenyl) hapten. MER, LPS and PPD enhanced the immune response of nude spleen cells to SRBC in vitro.

Adjuvants, Immunologic↗