A simple reliable system for studying antigen-specific murine T cell proliferation

Antigen-specific T cell proliferation can be readily elicited from the popliteal lymph node cells of mice which have received immunizations of antigen in the hind footpads. The advantages of our system over other published methods are (i) simplicity in method and materials, (ii) much improved reproducibility, (iii) negligible concomitant B cell proliferation, (iv) large degrees of antigen specific proliferation with very low background, and (v) complete dependence of the response on accessory cells or macrophages. These results were brought about by proper immunization procedures for mice and judicious choice of culture conditions. Our data show that the system is very suitable for the study of macrophage-T cell interaction in the induction of T cell proliferation as well as the genetic basis of responsiveness or non-responsiveness to protein and polypeptide antigens.

Effect of metal ions on growth and sporulation of Clostridium perfringens in a synthetic medium

All cells, whatever their origin, function in an essentially inorganic environment. In this environment, metal cations play an important role. Attempts were made in the present study to determine if different amounts of five metal ions (MG++, Fe++, Mn++, Zn++, Ca++) are needed for secondary metabolism of Clostridium perfringens than are needed for primary metabolism. Both the vegetative growth stage (primary metabolic stage) and spore stage (secondary metabolic stage) of Clostridium perfringens were studied. Endeavors were made to detect the effects of metal ions, if any, on growth and sporulation of the organisms. Mg++ was required for growth of vegetative cells and maintenance of normal cellular morphology, Fe++ was needed for sporulation as well as for vegetative growth, but the amount needed for spore formation was higher than that needed for growth. Ca++ was essential to refractility and heat-resistance of spores. Zn++ inhibited both growth and sporulation, if the Mg++ concentration was low. Mn++ was required for neither growth nor sporulation. For maximum heat-resistance of the spores, Ca++ plus unidentified organic substances were required.

Adenovirus type 12 DNA sequences in primary hamster tumors

In five out of six primary hamster tumors induced by adenovirus type 12, less than 55% of the adenovirus type 12 genome is present. Various fragments of the integrated viral DNA were present in non-equimolar amounts.

Functional heterogeneity in macrophages activated by Corynebacterium parvum: characterization of subpopulations with different activities in promoting immune responses and suppressing tumor cell growth

Peritoneal cells (PEC) from mice injected i.p. with heat-killed Corynebacterium parvum (CP) showed enhanced immunostimulatory (accessor or A cell) activity as measured by their ability to restore the immune responsiveness of nonadherent spleen cells to sheep erythrocytes (SRBC) and polymeric flagellin (POL) of Salmonella adelaide in vitro. This was true whether the PEC and nonadherent spleen cells were in direct contact or separated by a cell-impermeable membrane which allowed the free passage of soluble mediators. CP-activated PEC also exhibited greatly increased cytostatic activity against the growth of syngeneic tumor cells in vitro. After fractionation of the PEC according to cell size by velocity sedimentation, a separation of A cell activity from anti-tumor activity was observed. Although both these functions were associated with phagocytic cells of the monocyte-macrophage series, the highest A cell activity was found in fractions containing small and medium-sized macrophages, whereas the anti-tumor activity increased with cell size to a maximum with the largest macrophages. Thus, there is a relative increase of suppressive activity over stimulatory activity with an increase in cell size. Cytochemical and morphologic evidence suggests that the A cell-rich fractions contained small and medium-sized macrophages which were derived from newly arrived monocytes, whereas the large tumor-suppressive macrophages were relatively more differentiated.

Regulation of internodal lenght by peroxidase enzymes in grain sorghum

A relationship between height genes (dw locus) and perioxidase was demonstrated by extracting and determining peroxidase specific activity in internode tissue from different height isogenic lines of sorghum Sorghum bicolor (L.) Moench]. Tall plants (2 dwarf) had less peroxidase per gram tissue than their short counterparts (3 dwarf); their F1 offspring internodes were closer but had more peroxidase than the tall parent. Peroxidase in the F2 offspring was inversely related to their height and followed a simply-inherited pattern similar to that for height.Among different tissues analyzed, peroxidase concentration in roots was higher than in leaves and internodes, whole internode higher than in pith, and seed embryo higher than in endosperm. Peroxidase activity of nonviable seeds was negligible.Isoelectric focusing provided a more detailed peroxidase zymogram than did gel electrophoresis. Differences in peroxidase bands among tall and short parental plants, F1 and F2 segregating groups all appear to be reflected by intensity differences rather than by position or number of bands.Activities of nitrate reductase and acid phosphatase did not correlate with height. That finding provides a control and suggests that peroxidase activity is not associated with height by chance but may have a functional relationship.

Antigen recognition. IV. Discrimination by antigen-binding immunocompetent B cells between immunity and tolerance is determined by adherent cells

Mouse spleen cells capable of specifically binding intrinsically tritium-labeled polymerized flagellin (POL) (labeling by biosynthesis of flagellar protein) via IgM receptors were found to comprise a distinct population of about 20-50 cells per 10(6) lymphocytes. Evidence is presented that the majority of mouse spleen cells binding tritium-labeled POL undergoes blastogenesis after antigen capping, antigen shedding, and receptor reformation. Under conditions of tolerance induction in vitro, however, loss of antigen from the cell surface was inhibited. Such inhibition of antigen redistribution and shedding was reversed by a short pulse of colchicine and new antigen receptors were formed. In spite of this, colchicine had no effect on the tolerant state. However, tolerance could be broken, regardless of presence or absence of the alkaloid, with radioresistant theta-negative accessory (A) cells (adherent cells) from normal but not from tolerant spleen cell populations. "Tolerant" A cells, although they were incapable of cooperating in a response to POL, were capable of participating in a response to a second unrelated antigen. It is concluded that tolerance to POL in vitro is induced by mechanisms other than the physical blocking of bone marrow-derived (B) cell receptors by antigen. Most likely, the discrimination by the B cell between a tolerogenic and immunogenic signal is mediated by A cells.

Requirement for accessory cells in the antibody response to T cell-independent antigens in vitro

The antibody responses of mouse spleen cells in vitro to three thymus-independent (TI) antigens namely, polymeric flagellin (POL) of Salmonella adelaide, DNP-Ficoll and "soluble" sheep erythrocyte (SRBC) antigen, were found to be dependent on adherent accessory cells (A cells) but to a lesser degree than the response to intact SRBC. Evidence for this comes from selective depletion of A cells from spleen cells and reconstitution with A cell-rich populations. Thus, depletion of A cells by adherence on glass resulted in abolition of the response to SRBC leaving the response to POL intact. More thorough removal of A cells by treatment with carbonyl iron powder was required for appreciable reduction of the responses to POL, DNP-Ficoll and "soluble" SRBC. This reduction in responsiveness was not due to poor cell survival after A cell depletion or to the loss of immunocompetent cells since 1) the recoveries of viable cells in all cultures were similar; 2) the contents of theta- and Ig-bearing cells and tritium-labeled POL-binding cells were unaltered after carbonyl iron treatment, and 3) responsiveness was fully restored by the addition of irradiated and anti-theta-treated A cells from the peritoneal cavity or the spleen. Hence, the hitherto A cell independence of TI antigens on which some theories of B cell activation are based is a result of inadequate depletion procedures, and the minimal model for B cell activation must take into account two cell types: B cells and A cells.

Cell Electrophoresis of the Cellular Slime Mould Dictyostelium Discoideum

The reduction in cell surface charge density during the early stages of differentiation of the cellular slime mould, Dictyostelium discoideum, has been studied by the technique of cell electrophoresis. Using specific chemical reagents, it was shown that the cell surface negative charge was probably due to side chain carboxyl groups of proteins. During differentiation, there was a decrease in the density of these groups, accompanied by an increase in that of amino groups. The significance of this finding is discussed in relation to cell surface structure and cell differentiation.

Cell Electrophoresis of the Cellular Slime Mould Dictyostelium Discoideum

The reduction in the cell surface charge density of Dictyostelium discoideum during differentiation has been studied by the technique of cell electrophoresis. It was abolished under conditions in which cell aggregation was inhibited (e.g. low temperature, the presence of actinomycin D or cycloheximide). In the presence of nutrients incapable of supporting growth, cell aggregation occurred without a reduction in surface charge density. Cell adhesion in these aggregates was impaired, and a reduction in surface charge density appeared to be necessary for further development.

Brief treatment of exponential phase and aggregating cells with agents which disaggregate slugs failed to alter their electrophoretic mobilities. Low concentrations of magnesium chloride caused extensive agglutination, especially in aggregating cell suspensions, but little change in their electrophoretic mobilities. Magnesium chloride could agglutinate cells by association with cell surface components undetectable by cell electrophoresis. This, together with immunological evidence from other workers, supports the possibility of involvement of specific surface macromolecules in cellular slime mould aggregation. It was concluded that changes in surface charge density, though important for cell adhesion and morphogenesis, cannot account for all aspects of cell interactions in D. discoideum.