Interleukin 12, interferon gamma, and tumor necrosis factor alpha are the key cytokines of the generalized Shwartzman reaction.

The Shwartzman reaction is elicited by two injections of lipopolysaccharide (LPS) in mice. The priming LPS injection is given in the footpad, whereas the lethal LPS challenge is given intravenously 24 h later. The injection of interferon gamma (IFN-gamma) or interleukin 12 (IL-12) instead of the LPS priming injection induced the lethal reaction in mice further challenged with LPS. Antibodies against IFN-gamma when given together with the priming agent, prevented the lethal reaction in mice primed with either LPS, IL-12, or IFN-gamma. Antibodies against IL-12, when given together with the priming agent, prevented the lethal reaction in mice primed with either LPS or IL-12 but not with IFN-gamma. These results strongly suggest that LPS induces the release of IL-12, that IL-12 induces the production of IFN-gamma, and that IFN-gamma is the cytokine that primes macrophages and other cell types. Upon LPS challenge, the lethal Shwartzman reaction is induced by a massive production of inflammatory cytokines that act on the target sites already sensitized by IFN-gamma. If mixtures of TNF and IL-1 or mixtures of TNF and IFN-gamma are used to challenge mice previously primed with IFN-gamma or IL-12, mortality is induced. In the same conditions, the individual cytokines or a mixture of IL-1 and IFN-gamma do not replace the LPS challenge. When the mice are primed with LPS, the combination of TNF, IL-1, and IFN-gamma induced only a partial mortality incidence suggesting that the involvement of other LPS-induced factors.

Postfusion incompatibility in Physarum polycephalum: changes in protein pattern of a heterokaryon

The polypeptide patterns of two different strains of Physarum polycephalum, sensitive and killer, showed only minor differences on two-dimensional electrophoretograms. After heterologous fusion of the sensitive and killer plasmodia, newly formed proteins could be demonstrated which were not detectable in homologous fused plasmodia. The lethal reaction did not occur until after the aforementioned protein synthesis.

Postfusion incompatibility in Physarum polycephalum: involvement of membranes

Fusion of sensitive and killer plasmodia of Physarum polycephalum caused a change in membrane composition which did not occur after fusion of two sensitive plasmodia. This change, which was mainly the result of an increase in the synthesis of phosphatidylethanolamine, began 1.5 h after fusion. Heat production and oxygen consumption declined during the processes which underlie the lethal reaction which destroys the fused plasmodia of sensitive and killer strains.

The cestocidal effect of complement in normal and immune sera in vitro

SummaryThe effects of complement and/or specific antibodies on the larval and adult stages of Echinococcus granulosus were studied in vitro. Lysis and death of both protoscoleces and adult E. granulosus occurred within 10 min to 24 h in 50% fresh normal sera used as a source of complement, without the presence of specific antibodies. The lytic and lethal reaction was marked in fresh sera from guinea-pigs, calves, dogs, man and sheep, but only slight in fresh sera from English rabbits and horses. Guinea-pig sera were shown to be complement deficient after reacting with worms and all reactions were abolished after sera had been heated to 56 °C for 30 min. Fluorescent antibody studies failed to detect host antibodies at the parasite tegument. It is suggested that activation of the complement system occurs via the alternate pathway, that it acts independently of the immune system and that it is lethal to a wide range of cestode parasites.In contrast, marked agglutination/precipitation reactions with protoscoleces and precipitation reactions with adult E. granulosus were observed after incubation in heat inactivated 50% canine antisera, but not in normal sera. The antigen-antibody nature of these reactions was established by fluorescent antibody studies and the areas of antibody attack pinpointed. In spite of these reactions, worms remained healthy and active over a period of 8 days.

Varietal reactions of Trifolium subterraneum L. to Phaseolus virus 2 Pierce.

A number of varieties of subterranean clover (Trifolium subterraneum L.) were tested with a severe strain of Phaseolus virus 2 Pierce. Northam First Early, Dwalganup, and Pink Flowered gave lethal necrotic reactions while the rest developed mottles and chlorosis of different degrees of intensity. Reductions in the mean fresh weights of plants of five subterranean clover varieties ranged from 26.1 to 76.7 per cent. Epidermal cells of mottled leaves contained irregular aggregates of viroplasts stained by treatment with phloxine-trypan blue. Viroplasts in young tip leaves did not stain if the plants were held at temperatures below 44.6°F while those in mature basal leaves were not so affected. The lethal-reactors Northam First Early, Dwalganup, and Pink Flowered were resistant in the field to Phaseolus virus 2. With hand inoculation in the glass-house an average of 10 per cent. of plants of these varieties remained free from systemic infection, whereas all the plants of mottle-reacting varieties became systemically infected. The virus had a discontinous distribution in plants of lethal-reactors, compared with a continuous distribution in those of mottle-reactors such as Mount Barker. The lethal reaction is heritable in a dominant fashion in most crosses, so that the development of desirable new virus- resistant varieties is possible.

A STUDY OF THE BACTERICIDAL ACTION OF ULTRA VIOLET LIGHT

The simple conclusion of former investigators that the shorter the wave length of ultra violet light the greater the bactericidal action is in error. A study with measured monochromatic energy reveals a characteristic curve of bactericidal effectiveness with a striking maximum between 260 and 270 m.µ. The reciprocal of this abiotic energy curve suggests its close relation to specific light absorption by some single essential substance in the cell. Methods are described for determining the absorption curve, or absorption coefficients, of intact bacteria. These curves for S. aureus and B. coli have important points of similarity and of difference with the reciprocals of the curves of bactericidal incident energy, and point the way in a further search for the specific substance, or substances, involved in the lethal reaction.