When niacin requiring Escherichia coli (λ) was superinfected with λ phage during development of niacin deficiency, conversion of the injected molecule to covalently closed or nicked circles decreased in accordance with the reduction of cellular NAD (nicotinamide adenine dinucleotide) content. This finding suggested that host DNA ligase, which required NAD and induced the conversion, was not functional. In niacin deficient E. coli, vegetative growth of λoccurred, indicating that there were enough materials within the deficient cells to support multiplication of the phage. However, neither induction of prophage λ nor growth of superinfecting λC_I after treatment with mitomycin C was observed in E. coli (λ). This indicated that the immunity substance was active in niacin-deficient E. coli (λ) even after treatment with mitomycin C.

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Under certain conditions, Escherichia coli K12 cells lysogenic for λ can be made sensitive to free phage DNA without the addition of external helper phage. This competence depends on the phages released in the growth medium by spontaneous lysis. The kinetics of the decay of this competence are similar to the kinetics of cyclization of injected phage DNA.

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Polysomes specific for tobacco mosaic virus (TMV) infection were analyzed. Two to three days after inoculation of tobacco leaves with, TMV, polysomes of the large size, synthesizing TMV.antigenic protein were observed. Molecular weight of TMV-antigenic protein found under these conditions ranged from 2×104 to 6-8×104 daltons which might represent coat protein subunit and its trimer. Studies on the structure of polysomes hearing infecting RNA as messenger suggested that cistrons near the 3'-end of TMV-RNA was translated at first immediately after infection. These results favored the concept of a polycistronic translation of plant viral RNA, in contrast to a monocistronic translation observed in the mammalian system.

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Tolerogenic effect of soluble deaggregated bovine serum albumin (sBSA) on the γM and γG antibody responses was studied. Normal and tolerogen-treated animals were immunized with the intravenous injection of alum-precipitated BSA (net 0.1mg) and a bacterial endotoxin (0.01mg), since this immunizing procedure was the most adequate to elicit the strong responses of both types of antibodies. Both γM and γG responses were decreased evenly by a single injection of small dose (0.01 or 0.1mg) of sBSA. Larger doses (1mg or 5mg) caused the marked suppression of γM response, but the γG response was reduced only slightly. The tolerant state was facilitated by weekly injections of 0.1mg of sBSA, both γM and γG responses being abrogated profoundly by more than three injections. The induction of such a complete tolerance was not ascribed solely to either the total dose or the period of time between the first tolerogen injection and the challenge immunization, but to the retention of antigen more than a certain threshold amount in the body for some duration.

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Chemotherapeutic effect of rifampicin (RFP) and kanamycin (KM) to bacillary dysentery was evaluated using cynomolgus monkeys experimentally infected with Shigella flexneri 2a. Monkeys manifested typical symptoms of the disease after rectal administration of the bacilli. They were orally treated one or two days after challenge with a daily dose of 200mg of RFP or KM per animal for five consecutive days. These monkeys were investigated clinically, bacteriologically and histopathologically. A more rapid improvement of the stools from a bloody mucous to a normal with disappearance of the bacilli in stools was observed in RFP treatment as compared with KM treatment. Reappearance of bacilli in the stools was observed from six to eight days after the last administration with KM. A more significant inhibitory effect with RFP was observed in penetration and multiplication of the bacilli within host epithelial cells than with KM. A greater part of the animals treated with KM revealed, as seen in non-treated controls, catarrhalic colitis associated with penetration and multiplication of the bacilli in epithelial cells or in the lamina propria. However, no histological changes were observed in cases treated with RFP with the exception of one case with microfoci in the ileocecal valve.

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Restoration of impaired antibody response to sheep red blood cells (SRBC) in spleen cell cultures from mice treated with heterologous antilymphocyte globulin (ALG) was studied by adding normal cells from various sources, to explore the problems of cell-cooperation in anti-SRBC antibody response and the target of ALG. When spleen cells from ALG-treated mice were separated into macrophage-rich and lymphoid cell-rich subpopulations, only the latter was found to be impaired in the ability for anti-SRBC antibody response. Addition of even a small number of normal allogeneic spleen cells sufficiently restored the impaired anti-SRBC antibody response of the spleen cells from ALG-treated mice. By use of allo-antisera, most hemolysin plaque-forming cells (PFC) generated in such cultures were proved to be derived from the cells of ALG-treated mice. Restoration was also achieved by adding thymus-derived cells, which were obtained from spleens of mice heavily irradiated and repopulated with syngeneic thymus cells, or lymphoid cells directly collected from thymuses. All results indicate that ALG selectively depletes the thymus-derived antigen reactive cells (ARC) in the spleen cell population, and that ARC supplied from normal spleen or thymus can interact with plaque-forming cell precursors (PFCP) that remain intact in the spleen cell population of ALG-treated mice. The results also suggest that a single ARC interacts with more than one PFCP and makes them develop into PFC.

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Twenty-eight bacteriophage strains active on one or more species of Enterobacteriaceae were isolated from sewage and were classified into seven host range groups. Two isolates resemble S13, three isolates appear to be closely related to T_D, and one seems to be related to T even phages. Members of one host range group are active on three bacterial species, viz., Escherichia coli, Salmonella lyphimurium, and Shigella sonnei. Some of the E. coli K12 strains selected for resistance to phage HK019 are sensitive to S13 but not to φ×174.

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Water-in-oil emulsion (WOE) of the Freund's type and a bacterial endotoxin (ET) enhanced the antibody response of mice to bovine γ-globulin (EGG) in a different manner. WOE even without the antigen revealed an adjutant action when given prior to or simultaneously with the antigen, while ET was effectual when given simultaneously with or after the antigen. Thus, the concurrent administration of these two adjuyants either before or after the antigen secured enhancement. It was shown that ET facilitated IgM antibody formation. WOE including antigen (BGG-WOE) was found to form an 'antigen-depot' at the injected site. Antigen released bit by bit from this depot thus might supply a continuous stimulus for the antibody response. This was mimicked by a divided daily injection of a small amount of antigen without adjuvants. Surgical removal of the hind foot containing the depot resulted in reduction of the circulating antiboclt. The popliteal lymph node cells from mice given BGG-WOE via hind foot pads could adoptively immunize X-irradiated recipients without the additional administration of antigen, axillairy lymph node cells and spleen cells being unable to do so. ET was inadequate for this purpose. The morphological changes of the nodes secmed compatible with these results.

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A new, simple technique for the serum neutralization test with herpes simplex virus was devised. Thin discs made of solidified overlay medium containing about 2×10⁶PFU/ml of virus (VACS) were covered with 0.01ml of graded serum dilutions or control saline and placed on chick embryo cells with the serum-covered face down. A 90-mm monolayer dish received 8 such VACSs and then fixing overlay. The highest dilution of the serum which reduced confluent plaques to no or a few scattered plaques was taken as the endpoint. Incubation of the serum-covered VACSs at 37C for 1hr prior to inoculation could be omitted, since this procedure did not markedly increase the endpoint. A 2- to 4-fold fluctuation of the virus concentration had little influence on the endpoint. The standard deviation of the endpoint obtained was within±2-fold. The sensitivity of the test was about one-third that of the 50% plaque reduction method. Early sera containing predominantly complement-requiring neutralizing antibody ex-hibited considerable titers when tested by the new method even in the absence of complement, the reason for which remains unknown.

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