Substituted 9-benzyladenines: inhibitors of inflammation associated with the delayed hypersensitivity skin reaction

Members of a group of substituted 9-benzyladenines have been identified as effective inhibitors of inflammatory aspects of the delayed hypersensitivity skin reaction in the guinea-pig. Inhibitory activity was demonstrable in the efferent arc of the cell-mediated tuberculin and contact dermatitis (2,4-dinitrochlorobenzene) reactions. One of the compounds, 2-amino-9-benzyladenine, inhibited both turpentine-induced and histamine-induced inflammation in the skin. The toxicity and inhibitory activities of some of these compounds are discussed, and reference is made to the structurally related mercaptopurines.

Capillary density in developing and healing tuberculous lesions produced by BCG in rabbits. A quantitative study

Dermal tuberculous lesions were produced in rabbits by the intradermal injection of BCG. At various times after infection, anesthetized animals were perfused with a gelatin-colloidal carbon medium via the abdominal aorta. The capillary density of the nonnecrotic granulation tissue in the lesions was determined quantitatively by counting the capillaries under an ocular grid of a microscope. The capillary density in normal skin near the lesions was 3.8 plus or minus 0.5 in millimetersof capillary lengths per square millimeter in 250-mu tissue sections. The capillary density of the nonnecrotic tissue in BCGlesions averaged 6.1 plus or minus 0.6 mm/sq mm, an increase of 60%. The capillary density remained more or less constant as the BCG lesions grew and then regressed. The development of delayed hypersensitivity seemed to increase the capillary density, but this increase may have been a response to an extension of the necrosis at the time delayed hypersensitivity developed. Capillary densities in tuberculin reactions resembled those in BCG lesions. In the early stages, the increaseed capillary network of dermal BCG lesions was derived mainly from the subpapillary vascular plexus of the deep dermis supplied branches that surrounded the lower half of the caseous necrotic center and anastomosed with capillaries from the subpapillary plexus supplying the upper half. When the necrotic center extended, nearby capillaries thrombosed and in turn became necrotic. Peripherally, new capillaries formed and anastomosed with existing capillaries. From these vessels, mononuclear phagocytes emigrated, destroyed the tubercle bacilli, and enabled the lesion to heal. In the BCG lesions at all stages of development and healing, the capillary network in the nonnecrotic areas seemed adequate to supply and nourish the defense cells controlling the infection.

Quantitative measurement of delayed hypersensitivity in the guinea pig paw

To facilitate quantitative measurement of a delayed hypersensitivity reaction, a tuberculin reaction was produced in the paws of sensitized guinea pigs and the resulting edema estimated by one of the usual techniques. The edema formation was shown to be an expression of the delayed hypersensitivity reaction. Optimal conditions for this reaction were assessed. This model may be used for testing the influence of drugs on delayed hypersensitivity reactions.

Sensitivity to tuberculin and to PPD-Battey in two villages in Ponape District Trust Territory of the Pacific Islands

The reaction of the populations of two villages in Ponape District to PPD-Battey and to two tuberculin tests of different strengths was analyzed. The average annual incidence of infection in one village was estimated to be between seven and nine per cent per year; in the other village the incidence of infection was less than one per cent. Why these infection rates in the two villages were so different is not clear, but it is felt that the identification of the causative factor(s) may be considerable significance to the formulation of tuberculosis control policies in the district.

Skin testing of guinea pigs and footpad testing of mice with a new antigen for detecting delayed hypersensitivity to Cryptococcus neoformans

This study was undertaken to evaluate the potential of a cryptococcal culture filtrate antigen, cryptococcin C184, for detecting delayed hypersensitivity in Cryptococcus neoformans-injected animals. The antigen was tested on guinea pigs which had received saline or C. neoformans and on animals sensitized to Histoplasma capsulatum, Blastomyces dermatitidis, Candida albicans, or Sporothrix schenckii. A delayed-type hypersensitivity response was elicited by cryptococcin C184 in C. neoformans-injected guinea pigs, whereas no indurations or erythemas were seen at 48 h after skin testing of saline controls or heterologously sensitized guinea pigs. Besides being specific for Cryptococcus, the antigen showed a high degree of sensitivity and was reproducible. Footpad tests were conducted with the antigen on mice which had previously received either 10(5) viable C. neoformans cells or saline. Delayed hypersensitivity was indicated in the C. neoformans-injected mice by the increase in thickness of antigen-injected footpads when compared with the saline-injected footpads. In control mice, antigen- and saline-injected footpads were comparable in thickness 24 h after injection. Mice sensitized to B. dermatitidis were footpad tested with C184, and no cross-reactivity was demonstrated.

Relationship of antimicrobial cellular immunity to delayed hypersensitivity in Listeriosis

The relationship of antimicrobial cellular immunity to delayed hypersensitivity (DH) was studied in mice antigenically stimulated by living Listeria monocytogenes confined to diffusion chambers in peritoneal cavities or by subcutaneous inoculation of sublethal doses of the organism. Mice showed DH reactions when tested 6 days after inoculation, and reactions were positive for at least 90 days in some mice. DH also became established when the mice were stimulated by antigens diffusing from peritoneal chambers containing viable Listeria. Mice were categorized as DH positive or DH negative if they developed more or less than a 5% increase in foot volume 24 h after the injection of Listeria antigen. Some antigenically stimulated mice did not elicit the DH reaction. Consequently, the animals were arranged as immunized groups (DH positive and DH negative) and Listeria chamber implant groups (DH positive and DH negative). When challenged with L. monocytogenes, all four groups were significantly resistant as compared with controls. Thus, the in vivo tests for immunity and DH did not show direct correlation. The results suggested that antimicrobial cellular immunity can occur as a phenomenon independent of DH. Evidence for antimicrobial cellular immunity as the principle mechanism of resistance in murine listeriosis is discussed with consideration for possible heterogeneity of function by thymus-derived lymphocytes.

Demonstration of delayed hypersensitivity to Neisseria meningitidis

Guinea pigs were sensitized to Neisseria meningitidis group A by subcutaneous injection of viable meningococci. The animals were skin-tested with heat-killed N. meningitidis, a cell wall preparation of N. meningitidis, and a soluble somatic antigen prepared from the meningococci. Control skin-test substances included heat-killed Neisseria gonorrhoeae, heat-killed Escherichia coli, purified protein derivative, and Hank's balanced salt solution. Positive 24-h skin reactions, characterized by induration that measured greater than 5 × 5 mm (25 mm2), were produced only by heat-killed meningococci and with the cell wall preparations. The soluble somatic antigen produced only erythema. The meningococci also caused inhibition of migration of macrophages when peritoneal cells from the sensitized guinea pigs were used in the capillary tube MIF test. No inhibition of migration was produced with the control antigens. The delayed hypersensitivity was transferred with viable lymph node cells from the sensitized guinea pigs, but not with dead lymph node cells or with serum. The tests will be used to determine whether rabbits injected intravitreally with N. meningitidis develop delayed hypersensitivity.

Cutaneous basophil hypersensitivity in contact-sensitized guinea pigs. I. Transfer with immune serum

Cutaneous basophil hypersensitivity, an immune inflammatory reaction characterized by infiltrates of basophils and a delayed time-course, was studied in guinea pigs contact sensitized with oxazolone. Routine histological techniques, employing ordinary paraffin sections, were modified to study this reaction. When biopsies of contact lesions were processed by these methods dense infiltrates of basophils could be demonstrated. Animals sensitized with complete Freund's adjuvant emulsified with oxazolone-keyhole limpet hemocyanin conjugates also developed delayed-in-time responses to contact challenge with oxazolone but not to picryl chloride. These hapten-specific delayed-in-time reactions also contained substantial numbers of basophils. Transfer of serum from actively sensitized guinea pigs resulted in specific accumulation of basophils at challenge sites of recipients. Thus, in this experimental system, cutaneous basophil hypersensitivity was found to be a hapten-specific delayed-in-time reaction that could be transferred with immune serum.