Lectins as Probes to Pneumocystis carinii Surface Glycocomplexes

The binding characteristics of a panel of commercially available FITC-conjugated lectins to Pneumocystis carinii (Pc) were assessed by fluorescence microscopy and flow cytometry. Rat Pc obtained from infecteding homogenates were incubated with FTTC-conjugated lectins in a series of concentrations, counlerstained with propidium iodide, and analyzed for percent fluorescence and fluorescence intensity. All organisms bound concanavalin A and Wisteria floribunda agglutinin, 2 representatives of the glucose/mannose-binding group. From the lectin group specific for N-acctylglucosamine, Pc reacted more strongly with wheat germ agglutinin than with Solanum tuberosum agglutinin or Griffonia simpiicifolia II lectin. Pneumocystis treated with lectins specific for N-acetyl-D-galactosamine and galactose exhibited much variation; the cells reacted moderately well to soybean agglutinin and less to Bauhinia purpurea, Madura pomifera and Dolichos biflorus agglutinins and Giffonia simpiicifolia Hectin. Arachis hypogaea agglutinin, Viscum album agglutinin and Griffon'ui simpiicifolia I—β Section had not effect. The organisms reacted weakly with Ulex europeus I agglutinin which is specific for fucose and did not react with Limax ftavus lectin, which is specific for sialic acid. Competitive inhibition studies using relevant carbohydrates were performed to indicate that the positive reactions were specific. These studies should help to elucidate the mechanisms of attachment and pathogenesis of this organism.