Radiation, Infection, and Macrophage Function IV. Effect of Radiation on the Proliferative Abilities of Mononuclear Phagocytes in Tuberculous Lesions of Rabbits.

Rabbits were irradiated with 400 to 600 rads 2 to 3 days before they were infected with BCG or with virulent tubercle bacilli. Biopsies were periodically removed from the resulting lesions and incubated for 1 hr with (3)H-thymidine in vitro under hyperbaric oxygen. Twelve to 16 days after radiation there was a reduction in the percentage of mononuclear cells (macrophages and some lymphocytes) that had incorporated (3)H-thymidine in the lesions. At this time, the lesions of the irradiated group were smaller than those of controls. These results can be explained by the reduction in the number of new mononuclear cells that entered the lesions of the irradiated group and support the tenet that local mononuclear cell division occurs mainly in cells that have recently emigrated from the blood stream. An alternate, but less likely, explanation of these results would be that radiation caused the bone marrow to release a higher percentage of "defective" mononuclear cells that were unable to divide, i.e., incorporate (3)H-thymidine, in the lesions. The reduction produced by radiation in both local cell infiltration and local cell division would decrease the number of macrophages available to control the tuberculous infection in the host.

Effect of formaldehyde on the immunogenicity of staphylococcal enterotoxin B for Macaca mulatta.

Monkeys were immunized with enterotoxin and enterotoxoid by intracutaneous injection or by feeding. Identical schedules were used to compare the effectiveness of the two antigens and the two routes. Enterotoxin administered intracutaneously was the most effective antigen, whereas oral administration of enterotoxoid was least effective. Intracutaneous injection of toxoid and oral feeding of toxin were intermediate and not too dissimilar in effectiveness. Antibody titers and protection persisted for at least 1 year at a relatively high level. Monkeys that had preimmunization hemagglutinins showed an anamnestic response after immunization. The development of protection and the appearance of antibodies subsequent to feeding toxin or toxoid suggest that ingestion of food contaminated by staphylococci or their metabolites may be one cause for the appearance of antitoxin in the serum of supposedly unexposed animals and man.

Permanent turbidity standards.

Permanent turbidity reference standards suitable for measurement of microbial suspensions were prepared by suspending finely divided titanium dioxide in aryl sulfonamide-formaldehyde or methylstyrene resins. Turbidities of these standards, adjusted to a useful range for microbiological and immunological studies, were compared with other reference standards in use today. Tube holders for a Coleman Photonephelometer and a Nepho-Colorimeter were modified to eliminate the water well and to allow use of optically standardized 10-, 16-, or 18-mm test tubes. The standards and the tube holders have been used satisfactorily for more than 12 years.