[Cryo-agglutination, complement & anticomplementary activity].

Recombinant human surfactant protein D (SP-D) expressed in Escherichia coli, consisting of the head and neck regions of the native molecule, bound to all strains of Streptococcus pneumoniae that were tested, but the extent of binding varied between strains of differing capsular serotypes. The recombinant protein expressed in the yeast Pichia pastoris did not bind. Full-length native SP-D aggregated pneumococci in a calcium-dependent manner that was inhibited by maltose acting as a competitive sugar. The ability of SP-D to modulate the uptake and killing of pneumococci by human neutrophils was also addressed. Neither recombinant truncated SP-D nor native full-length SP-D enhanced the killing of pneumococci by human neutrophils. Aggregation of pneumococci varied not only between strains of the same multilocus sequence type and different serotypes but also between strains of the same serotype. However, use of recombinant strains in which the serotype had been changed showed that the degree of aggregation was influenced by the capsular type. Indeed, a 19F serotype strain which was not aggregated by SP-D did exhibit aggregation when the original isogenic strain was capsule switched to capsular serotype 3. However, although our results show that SP-D is capable of aggregating most pneumococci, no correlation between the degree of aggregation and the capsule or multilocus sequence type of the pneumococcus was clearly apparent. Therefore, although the capsule serotype is not the only determinant of aggregation by SP-D, the data presented here indicate that it does have a role to play.

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PubMed2003

Gliadin cytotoxicity and in vitro cell cultures.

Interest in celiac disease, a common enteropathy in Europe and the USA (1/200) caused by the dietary ingestion of gluten in susceptible subjects, has increased over the last few years. Its pathogenesis is still not completely clear, but it certainly involves immune-mediated mechanisms. Although a number of studies have been published concerning the role of T cells in inducing intestinal damage, little is known about the early stages in which gliadin (the toxic component of gluten) starts the whole process. In vitro two- and three-dimensional (multicellular spheroid) cell cultures are a simple and useful means of studying the direct cellular effects of gliadin and other "toxic" cereal peptides. Furthermore, in addition to improving our understanding of pathogenetic mechanisms, cell cultures can also be used to test modified peptides that could replace the toxic components present in the foods that celiac patients must avoid.

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