Local footpad infection in mouse was investigated with 55 clinically isolated strains of Staphylococcus aureus. When 10⁷ viable cells were inoculated into the footpad, local swelling and bacterial growth resulted after 24 hr. With a dose of 10⁶ cells, moderate swelling was observed after a few hours but the reaction had almost disappeared after 24 hr. About 75% of the staphylococcal strains tested caused footpad edema in mice at doses of 10⁷ cells. A statistical comparison of the virulence of the organisms on intravenous and intraperitoneal injection with that in inducing footpad swelling is also reported.

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Pretreatment of mouse L cells with interferon (IF) enhanced IF production in response to polyinosinic-polycytidylic acid (poly I·poly C). Post-treatment of cells with IF caused no significant enhancement of IF production. The enhancing effect of IF pretreatment (priming) reached a maximum after incubation with IF (10 or 100 units/ml) for 4-6 hr at 37 C, but this effect was absent when the incubation was done at 4 C. Cells which were incubated for additional several hours at 37 C after IF pretreatment at 4 C did not develop the primed state nor the antiviral state. The presence of protein synthesis inhibitors during the IF pretreatment depressed, though not completely, the development of the primed state. The residual priming effect was lost when the cells were incubated with the inhibitors at 37 C for 2 hr before they were exposed to poly I·poly C. There was no significant difference in the binding rate of poly I·poly C to cells between IF-treated and untreated cells. The degradation rate of cell-bound poly I·poly C and its sensitivity to exogenous pancreatic ribonuclcase in the pretreated cells were also similar to those in the untreated cells.

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Bactericidal activities of peripheral white blood cells obtained from patients and from healthy persons were examined in vitro. The results obtained are summarized as follows. 1. Peripheral white blood cells from patients receiving corticosteroid and radiation therapy showed decreased levels of intracellular bactericidal activities against Staphylococcus aureus. The leukocytes from almost all patients examined displayed intense activities of intracellular bacterial killing against Streptococcus pyogenes. 2. Only polymorphonuclear leukocytes (PMNs) and macrophages obtained from patients in severe stages of diabetes mellitus exhibited decreased levels of intracellular bactericidal activities against S. aureus. 3. The leukocytes from all patients examined exhibited the same levels of intracellular bactericidal effects against S. pyogenes as leukocytes from healthy persons. 4. Pseudomonas aeruginosa, which was phagocytized by PMNs obtained from healthy persons, demonstrated a remarkable degree of resistance to any intracellular bactericidal effect.

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Peripheral blood leukocytes from patients given corticosteroid or radiation therapy, as well as patients with bacterial or viral infections, were studied with regard to the selected enzyme activities of the hexose monophosphate shunt (HMS). Glucose-6-phosphate dehydrogenase (G-6-PD), 6-phosphogluconate dehydrogenase (6-PGD) and reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase were assayed spectrophotometrically on mixed leukocyte suspensions in isotonic glycerol. Enzyme activities of G-6-PD and NADPH oxidase in patients receiving corticosteroid or radiation therapy were significantly lower than the enzyme activity of 6-PGD. In patients with bacterial infections, activities of the three enzymes increased but in patients with viral infections, only the activities of NADPH oxidase and G-6-PD were slightly decreased. Nitroblue tetrazolium (NBT) dyereducing activities of neutrophils from patients receiving corticosteroid or radiation therapy were attenuated which coincides with the reduced activities of HMS enzymes. From these results, it is likely that the reduced activities of intraleukocytic HMS enzymes of patients receiving corticosteroid or radiation therapy are correlated with intracellular bactericidal activities which might result from the attenuated level of hydrogen peroxide production.

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Cell wall preparations of Bacillus anthracis, strain Pasteur No. 2-H, were treated with heat or with acetone and ether. Both of the treated cell walls preparations inactivated γ phage. The centrifuged supernatant of the heat-treated cell walls was fractionated on Sephadex G-200, and four fractions containing reducing sugars were obtained. The first fraction had the phage-inactivating activity. On the other hand, the fourth fraction had no phage-inactivating activity, but strongly inhibited phage adsorption to the cell walls. In the fourth fraction, glutamic acid, alanine, 2, 6-diaminopimelic acid and glucosamine were detected by paper chromatography after acid hydrolysis. Authentic D, L-2, 6-diaminopimelic acid and D-glucosamine markedly inhibited phage adsorption to the cell walls. D-Galactosamine, D-mannosamine and L-lysine also showed similar activities. Results suggest the possibility that one or a combination of these substances defines the characteristics of phage adsorption to the cell walls of B. anthracis, strain Pasteur No. 2-H.

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Comparative studies were made on the generalized transducing bacteriophages of Proteus mirabilis φm (Nakaya and Rownd), π1 (Bohme), and a clear plaque-forming mutant φm-c, derived from φm. Electron microscopic observations revealed that these phages were morphologically identical, indicating that they belonged to the group C of Bradley's classification, or to the type Cl of Ackermann's classification. Phages φm and π1 formed characteristic turbid plaques different from each other, and the plaques of π1 were smaller in size than those of φm. The plaques of phage φm-c were clear and also were the largest in size among those studied. Average latent periods of φm and π1 were 70 and 60 min, respectively. Average burst size was found to be 30 and 10 plaque-forming units per infected cell for φm and π1, respectively. It was confirmed by cross neutralization tests that φm and π1 differed serologically from each other. The host range of the two phages also differed, and phage φm was more sensitive to heat than π1. These results indicate that phages φm and π1 are different types of phages. Majority of the properties of phage φm-c were nearly identical with those of phage φm except that the multiplication of φm-c was more strongly inhibited by methylene blue than that of φm and π1. Phage φm-c is considered to be a clear mutant of φm.

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Antigenic analyses of Lactobacillus fermenti were carried out by double immunodiffusion in agar using extracts prepared with cold trichloroacetic acid (TCA) or hot dilute hydrochloric acid (HCl). A common antigen of L. fermenti, designated as antigen f by the author, was extracted from whole cells with dilute HCl, but not with TCA. The antigen f was also observed in Lactobacillus casei. In addition, all strains isolated from human saliva contained antigen 6 in their cell walls, while the antigen was not observed in most of the isolates from human feces. Therefore, L. fermenti could be divided into two subgroups based upon the existence of antigen 6. Antigen 7 which was demonstrated in some strains of L. fermenti was shared by other species of lactobacilli belonging to the serological groups D and E. The common antigen 3 found in lactobacilli was extracted from all strains of L. fermenti. Sugar components of cell walls were mainly galactose, glucose and glucosamine (including N-acetylglucosamine), but a small amount of rhamnose was present in the cell wall of only one strain. Inhibition tests with various sugars showed that the serologically active sugars were galactose for antigen f and glucose for antigen 6.

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Mechanisms of nonspecific elicitation of anti-sheep erythrocyte (SRBC) hemolytic antibody plaqueforming cells (PFC) in mouse spleens with an injection of bacterial endotoxin (lipopolysaccharide (LPS)) were studied in comparison with the genesis of naturally occurring ‘background’ PFC in normal mouse spleens and of rapidly arising PFC in mouse spleens after immunization with SRBC. The cytokinetic pattern of anti-SRBC PFC response after an injection of LPS was quite different from that of the response elicited after immunization with SRBC. In addition, even though LPS nonspecifically elicited anti-SRBC PFC response in mice, LPS could not confer any immunological memory on mouse immunocytes for a ‘secondary-type’ anti-SRBC PFC response to restimulation with LPS or SRBC. The administration of rabbit anti-mouse thymocyte immunoglobulin or anti-SRBC antiserum in mice markedly suppressed the PFC response after immunization with SRBC, but did not do so after stimulation with LPS. Neonatally thymectomized mice could still respond to stimulation with LPS, producing anti-SRBC PFC in their spleens. Injections of actinomycin D or cyclophosphamide into mice resulted in obvious reductions of the PFC responses elicited by either LPS or SRBC. However, injections of these immunosuppressive antisera or drugs did not affect the number of anti-SRBC PFC in normal mouse spleens. These results suggest that the geneses of anti-SRBC PFC developed under different conditions, i.e., background PFC, LPS-stimulated PFC, and antigen-stimulated PFC, are quite different from each other, and that the nonspecific elicitation of anti-SRBC PFC by LPS does not require the helper function of T lymphocytes. No obvious difference, however, was observed in the time of ontogenic maturation among these three different anti-SRBC PFC in the mouse spleens judging from when they were first manifested after birth.

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Macrophages from mice were infected with Neisseria gonorrhoeae type 1 cells, and their ultrastructure was studied by electron microscopy. The macrophages showed various stages of engulfment and digestion of gonococci 2 hr after infection. Infected macrophages seemed to develop pseudopodia for phagocytosis, and could engulf more than 30 gonococcal cells. Some engulfed bacteria appeared morphologically intact, while others appeared lysed and some structures resembling the L form of N. gonorrhoeae were also seen. These observations suggest that gonococcal cells may be able to survive intracellularly with normal or altered forms of morphology, and that macrophages containing these bacteria may disseminate gonococcal infection in man.

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Guinea pigs experimentally infected with Mycoplasma pneumoniae or immunized with the organism in combination with Freund's complete adjuvant developed a delayed hypersensitive skin reaction following on intradermal injection of the M. pneumoniae antigen. The amount of protein necessary to produce the delayed skin reaction was as low as 0.01 μg. When the sonicated whole cells were extracted with aqueous acetone, the delayed skin reactivity was found mostly in the acetone insoluble (lipid-depleted) fraction. On the other hand, the lipid fraction which was isolated by a chloroform-methanol extraction of the acetone-soluble fraction and had a high titer of complement-fixing activity, exhibited little delayed skin reactivity. The lipid-depleted antigens as the whole cell antigens produced delayed skin reactivities in human patients.

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