Synthesis of a C-glycoside analogue of beta-D-galactosyl hydroxynorvaline and its use in immunological studies.

A C-linked isostere of beta-D-galactosylated hydroxynorvaline has been prepared in eight steps from per-O-benzylated galactopyranolactone. Addition of a homoallylic Grignard reagent to the lactone, reduction of the resulting hemiacetal with triethylsilane, and a Wittig reaction with Garner's aldehyde were key steps in this synthesis. The C-linked building block was then incorporated at position 264 into the fragment CII(256--270) from typeII collagen by solid-phase synthesis using a combination of the tert-butoxycarbonyl (Boc) and 9-fluorenylmethoxycarbonyl (Fmoc) protective group strategies. Deprotection of the benzylated C-linked galactosyl moiety was achieved simultaneously with cleavage of the glycopeptide from the solid phase by using triethylsilyl trifluoromethanesulfonate in TFA. Helper T-cell hybridomas obtained in a mouse model for rheumatoid arthritis responded to the C-linked glycopeptide when presented by classII MHC molecules. However, 10- to 20-fold higher concentrations were required as compared to when O-linked beta-D-galactosylated hydroxynorvaline or hydroxylysine (Hyl) were present at position 264 of CII(256--270). Thus, replacement of a single oxygen atom by a methylene group in the carbohydrate moiety of a glycopeptide antigen had a substantial influence on the T-cell response. This reveals that T cells are able to recognize the carbohydrate moiety of glycopeptide antigens with high specificity. Finally, the results suggest that structural modifications of beta-D-Gal-Hyl(264) in CII(256--270) may give altered peptide ligands that can be used for induction of tolerance in autoimmune rheumatoid arthritis.

Laser capture microdissection of single cells from complex tissues.

Laser capture microdissection (LCM) is a new method used to select and procure cell clusters from tissue sections. Once captured, the DNA, RNA or protein can be easily extracted from the isolated cells and analyzed by conventional PCR, reverse transcription (RT)-PCR or polyacrylamide gel electrophoresis, including protein zymography for specific macromolecular changes. In LCM, a thermoplastic polymer coating [ethylene vinyl acetate (EVA)] attached to a rigid support is placed in contact with a tissue section. The EVA polymer over microscopically selected cell clusters is precisely activated by a near-infrared laser pulse and then bonds to the targeted area. Removal of the EVA and its support from the tissue section procures the selected cell aggregates for molecular analysis. This initial NIH LCM approach using a flat transfer EVA film has been recently commercialized and has proven to be an effective routine microdissection technique for subsequent macromolecular analysis in many laboratories around the world. However, reliable and precise capture of individual cells from tissue sections has been difficult to perform with the current LCM instruments. In this report, we describe the capture of individual cells with a new NIH LCM microscope, which epi-irradiates the EVA polymer overlying individual cells with 1-ms laser pulses focused to 6 microns. A computer-controlled arm precisely positions a 40-micron-wide strip of a cylindrical EVA surface onto a sample with a light contact force (ca. 0.1 g). The small contact force and contact area on the film on the sample diminishes nonspecific transfer to negligible levels. By slightly rotating the cylinder to provide a renewable transfer surface, concentration of a distinct cell type on a single cylinder is possible. Using this novel adaptation, we demonstrate the rapid and practical capture of single cells from different types of tissue sections, including immunostained cells.