Measles, mumps, rubella vaccine administration in egg-sensitive children: systemic reactions during vaccine desensitization.

In egg-sensitive children, measles-mumps-rubella (MMR) vaccination may cause acute allergic reactions; therefore, current recommendations are to perform skin testing with the commercial vaccine before administration to egg-allergic children. In children with positive skin tests, desensitization with the measles-mumps-rubella vaccine should be done in order to administer a full dose of the vaccine. Twelve egg-allergic children, aged 12 months to 5 years of age, were referred to our pediatric allergy clinic for MMR administration over a 20-month period. Three children had positive skin prick or intradermal tests to the MMR vaccine. Two of these three patients experienced systemic hypersensitivity reactions while undergoing desensitization to the MMR. All reactions occurred with injections of the undiluted vaccine. Based upon this experience, we recommend that egg-allergic children should continue to have cutaneous tests done to the MMR vaccine and careful observation during desensitization in those children with positive skin tests.

Particle digestibility is required for induction of the phosphatidylserine recognition mechanism used by murine macrophages to phagocytose apoptotic cells.

One of the characteristic features of programmed cell death in vivo is the rapid recognition and removal of apoptotic cells by macrophages. Although there are several potential mechanisms by which the macrophage can identify a cell as apoptotic, it has been shown recently that murine-elicited macrophages stereospecifically recognize phosphatidylserine (PS) exposed on the surface of apoptotic cells. The particulate stimulus, beta-1, 3-glucan, stimulates bone marrow-derived macrophages to express several characteristics of inflammatory macrophages, and induced these cells to recognize PS on apoptotic cells; this activity was correlated with the ability to form rosettes with PS-expressing RBC. Induction of PS recognition in bone marrow-derived macrophages was associated with digestibility of the stimulus, because L, but not D amino acid particles or latex, were able to stimulate macrophage recognition of PS. The requirement for digestibility could be bypassed by the addition of exogenous TGF-beta, which induced macrophage recognition of PS after stimulation with either latex or D amino acid particles. That endogenously produced TGF-beta played a role in the glucan-stimulated response was indicated by the ability of anti-TGF-beta antibodies to inhibit digestible particle-induced recognition of PS. The induction of the PS recognition mechanism correlated well with the expression of other markers for the inflammatory phenotype. These studies indicate that the PS receptor may be a marker for the inflammatory phenotype, which appears to be induced by the phagocytosis of particulate digestible stimuli. Endogenously produced TGF-beta is suggested to play an autocrine or paracrine priming role in the induction of the PS receptor.

Development of functional diversity in mouse macrophages. Mutual exclusion of two phenotypic states.

The objective of this study was to investigate the mechanisms that contribute to the generation of macrophage functional diversity. Exposure of mouse bone marrow-derived macrophages to beta-1,3-glucan, a particulate inflammatory stimulus, or polyinosinate-polycytidylate (poly[I:C]), a stimulus of macrophage cytocidal activation, induced distinct and stimulus-specific patterns of gene expression. These changes were characterized by an up-regulation of the expression of the acid hydrolase beta-glucuronidase and platelet-derived growth factor B following incubation with beta-1,3-glucan and a stimulation of the expression of the complement component Bf, beta-interferon, and the reactive nitrogen intermediates NO2/NO3 during incubation with poly[I:C]. The induction of Bf expression by poly[I:C] could not be explained on the basis of distinct subpopulations of cells since in situ hybridization with a mouse Bf cRNA probe revealed a uniform and substantial increase in Bf expression by the entire population of cells. Incubation of macrophages with beta-1,3-glucan before stimulation with poly[I:C] was found to strongly attenuate the expression of Bf and beta-interferon. Conversely, incubation with poly[I:C] prior to exposure to beta-1,3-glucan substantially blocked the stimulation of beta-glucuronidase and platelet-derived growth factor B expression, indicating that these two responses were expressed in a mutually antagonistic fashion. However, after removal of either stimulus and following a period in which the primary response was allowed to decay, the cells regained their capacity to subsequently respond to either the same stimulus or to a different stimulus. Collectively, these findings indicate, first, that the heterogeneity of gene expression seen in response to poly[I:C] represents an adaptive response of the entire macrophage population rather than the restricted responses of distinct subpopulations of cells. Second, macrophages respond to these stimuli in a sequential fashion. These findings thus have a significant bearing on our understanding of the regulation of macrophage heterogeneity in host defense.

Bacillus cereus electron transport and proton motive force during aerotaxis.

Aerotaxis (migration towards oxygen) of Bacillus cereus M63, a motile strain, was inhibited by potassium cyanide and 2-heptyl-4-hydroxyquinoline N-oxide, indicating a requirement for both the terminal oxidase (cytochrome aa3) and the cytochrome b segment of the electron transport system. The concentration of oxygen that gave a half-maximal aerotactic response (K0.5) was 0.31 microM, which was similar to the Km for respiration (0.80 microM). The proton motive force increased from -135 to -177 mV when anaerobic cells were aerated, and it is proposed that the signal for aerotaxis is the increase in proton motive force that results from increased respiration. A strain of B. cereus T initially used in this study was immotile, grew as long chains of cells, and was deficient in autolytic enzyme. B. cereus M63 is a spontaneous derivative of B. cereus T that has normal motility.

Cytochrome o as a terminal oxidase and receptor for aerotaxis in Salmonella typhimurium.

Cytochrome o was the only oxidase of the electron transport system that was present in exponentially growing Salmonella typhimurium ST1. Identification of cytochrome o was made by the (CO-reduced)-minus-(reduced) difference spectra and by the photochemical action spectrum of the relief, by light, of CO-inhibited respiration. Cytochrome o also functioned as the receptor for chemotaxis to oxygen (aerotaxis). The concentration of oxygen that elicits the maximum response for aerotaxis (0.7 microM) was similar to the Km for respiration (0.74 microM), and both aerotaxis and respiration were blocked 5 mM KCN.

Aerotaxis in Salmonella typhimurium: role of electron transport.

Sensory transduction in aerotaxis required electron transport, in contrast to chemotaxis, which is independent of electron transport. Assays for aerotaxis were developed by employing spatial and temporal oxygen gradients imposed independently of respiration. By varying the step increase in oxygen concentration in the temporal assay, the dose-response relationship was obtained for aerotaxis in Salmonella typhimurium. A half-maximal response at 0.4 microM oxygen and inhibition by 5 mM KCN suggested that the "receptor" for aerotaxis is cytochrome o. The response was independent of adenosine triphosphate formation via oxidative phosphorylation but did correlate with changes in membrane potential monitored with the fluorescent cyanine dye diS-C3-(5). Nitrate and fumarate, which are alternative electron acceptors for the respiratory chain in S. typhimurium, inhibited aerotaxis when nitrate reductase and fumarate reductase were induced. These results support the hypothesis that taxis to oxygen, nitrate, and fumarate is mediated by the electron transport system and by changes in the proton motive force. Aerotaxis was normal in Escherichia coli mutants that were defective in the tsr, tar, or trg genes; in S. typhimurium, oxygen did not stimulate methylation of the products of these genes. A cheC mutant which shows an inverse response to chemoattractants also gave an inverse response to oxygen. Therefore, aerotaxis is transduced by a distinct and unidentified signally protein but is focused into the common chemosensory pathway before the step involving the cheC product. When S. typhimurium became anaerobic, the decreased proton motive force from glycolysis supported slow swimming but not tumbling, indicating that a minimum proton motive force was required for tumbling. The bacteria rapidly adapted to the anaerobic condition and resumed tumbling after about 3 min. The adaptation period was much shorter when the bacteria had been previously grown anaerobically.