Temperature dependence of transfer was examined with ten R plasmids originating from clinical isolates of Salmonella. Six of the plasmids were thermosensitive upon transfer, five of which were originally harbored in S. typhimurium and the remaining one in S. derby. One of these plasmids, pNR502, which conferred resistance to kanamycin, streptomycin (Sm) and tetracycline (Tc) on its host was stably maintained both in Salmonella and Escherichia coli at either 30, 37, or 43 C. Another plasmid, pNR516, which was resistant to chloramphenicol, sulfathiazole, Sm and Tc, was slightly unstable only at 43 C. The remaining four plasmids, pNR503, pNR510, pNR512 and pNR514, conferred resistance to Sm and Tc. Of these plasmids, the former two were stably maintained at both 30 and 37 C, but were unstable at 43 C. The latter two were slightly unstable at the lower temperatures and considerably unstable at 43 C. Kinetics of the transfer of the plasmid pNR503 revealed that the efficiency of transfer of the plasmid between E. coli strains was affected not only by the temperature of the conjugation but also by the preincubation temperature of the donor culture before the conjugation.

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The binding of radioactive glucan to Streptococcus mutans cells, which are agglutinated by dextrans, was examined. The glucan was synthesized from sucrose by extracellular glucosyltransferases from S. mutans FA-1 and was highly branched at C-3 and C-6 of D-glucose residues, containing 17% of α (1→3) inter-chain residues. Binding of glucan to whole cells of S. mutans OMZ-176, which were agglutinated by addition of glucan or Dextran T2000, was irreversible and followed saturation type kinetics; saturation was achieved at approximately 110 ng of glucan per ml. About 14 ng of glucan were bound per mg of the cells at the saturated concentration. The heated cells of this organism, however, had a relatively low ability of glucan-binding, compared with the freshly prepared and lyophilized cells. Binding to the heated cells was entirely of a non-saturation type. Binding of Dextran T2000 or T10 was determined by competition between the labeled glucan and unlabeled Dextrans for the binding site (s). Both Dextrans and glucan from S. mutans FA-1 were bound to the same site (s). Other organisms, which did not undergo glucan-and Dextran-induced agglutination, had a relatively lower ability of glucan-binding than S. mutans, which was agglutinated.

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In an attempt to determine whether mouse cytomegalovirus (MCMV) requires thymidine kinase (TK) for replication and whether it induces TK, TK-deficient mouse cells were isolated and used as host cells for MCMV. Mutant cells resistant to 200 μg/ml of 5-Bromodeoxyuridine (BUdR) were selected from SV40-transformed mouse cells, mks-A TU-7, by propagating the cells in the presence of varying concentrations of BUdR graded by serial 2-fold increments. The mutant cells, designated as TU-7 BU, showed a very low TK activity (less than 1/20 that of mks-A TU-7). Herpes simplex virus type 1 (HSV-1) replicated in starved as well as in unstarved TU-7 BU, whereas MCMV could replicate only in growing TU-7 BU and could not form plaques in monolayers of mks-A TU-7 or TU-7 BU. HSV-1 infection enhanced TK activity equally in both mks-A TU-7 and TU-7 BU. In contrast, TK activity of MCMV-infected mks-A TU-7 was lower than that of uninfected cells or cells inoculated with UV-inactivated virus. In addition, TK activity of the MCMV-infected TU-7 BU remained minimal without showing any increase. The replication of HSV-1 was completely inhibited in the presence of BUdR (10 μg/ml), whereas MCMV could replicate even in the presence of 50 μg/ml of BUdR. The results indicate that MCMV neither requires TK nor induces TK activity in the infected cells.

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The formation of cowpox virus-specific cell surface antigen (CPV S-ag) was significantly enhanced by double infection with HVJ (Sendai virus). Simultaneous double infection, superinfection with HVJ and superinfection with CPV of cells persistently infected with HVJ similarly enhanced the formation of CPV S-ag, while pre-infection with HVJ was ineffective. To be effective, cells must be infected at a m.o.i. of ≥ 1.0 and HVJ gene functions had to be expressed.
The HVJ-infected cell extracts had an ability to accelerate uncoating (or degradation) of CPV, causing an early increase and a subsequent decrease in the infectivity of CPV. This activity reached a maximum 4-6 hr after HVJ infection, the increase paralleling enhancement of the total activity of several cellular enzymes. Addition of puromycin abolished the increase of these activities and the formation of CPV S-ag.
Thus, the double infection with HVJ of CPV-infected cells induces an enhancement of CPV S-ag formation presumably as a consequence of activation of cellular enzymes which in turn accelerates uncoating of CPV.

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Newcastle disease virus grown in embryonated eggs was separated and purified by sucrose density gradient centrifugation into two distinct types of particles, B and T, the former being normal virus particles with high activities of hemagglutination, hemolysis, neuraminidase and infectivity, the latter being non-infectious virus particles with low activities of hemolysis and neuraminidase but high hemagglutination activity. B and T particles were shown to share a common antigen by immunodiffusion test. T particles were deficient in viral RNA, since they contained only 13s RNA in a small amount, whereas B particles possessed a large amount of 57s RNA and a small amount of 13s RNA. T particles interfered with the multiplication of normal Newcastle disease virus in primary cultures of chick embryo cells.

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A leukocyte migration inhibition test (LMIT) utilizing the agarose gel technique was performed with native DNA as an antigen in ten patients with systemic lupus erythematosus (SLE) and five normal subjects. Irrespective of disease activity, supernatants obtained at different time intervals during lymphocyte culture in eight patients with SLE showed significant alteration of migration, either enhancement or inhibition, of normal leukocytes. However, supernatants in the control experiments produced no significant alteration of migration. Polyacrylamide gel electrophoresis of supernatants obtained from the SLE group revealed that the inhibitory activity was present in the albumin region, whereas the enhancement activity was found in the β-globulin region. These results indicate that the hitherto employed estimation of the leukocyte migration inhibition test based on the total activity of these two factors is insufficient for accurate evaluation of chemical mediators from sensitized lymphocytes and that the separation of these two factors may be important for a greater understanding of cellular immunity.

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The expression of antibody-producing capacities against hamster erythrocytes (HRBC), known to be weakly immunogenic in mice, was compared among conventional, SPF, germfree and antigen-free mice.
ICR strain germfree and antigen-free mice showed antibody production to HRBC comparable to that in conventional or specific-pathogen-free (SPF) mice.
In the NC strain, some of the conventional mice produced low titers of antibody after a single injection of HRBC, but none of the germfree mice showed such a transient antibody production. In the ICR-KIG strain, which was selected from the colony-bred ICR strain, antibodies with high titers were produced after a single injection of HRBC under both conventional and germfree conditions. The onset of conversion from 2-mercaptoethanol (2-ME) sensitive to 2-ME resistant antibody after a single injection of HRBC was not delayed in the germfree mice when compared with the conventional or SPF mice.
Antibody production to sheep erythrocytes (SRBC), known to be highly immunogenic in mice, was not influenced by exogeneous stimulation from microorganisms or diet. No differences in antibody production to SRBC were detected irrespective of the maintenance conditions of the mice.
Stimulation with microorganisms or diet may not be required as essential elements for the maturation of antibody-producing capacities, but such a stimulation appears to modify the antibody response. The modifying effect was more prominent in the antibody response against weakly immunogenic antigens than against highly immunogenic ones.

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