Unusual surface distribution of concanavalin A reflects a cytoskeletal defect in neutrophils in Shwachman's syndrome.

Schwachman's syndrome is characterised by pancreatic insufficiency and frequent infections. Absolute polymorphonuclear leucocyte (PMN) counts are low in many patients, and the PMN show abnormal chemotaxis. It was postulated that a cytoskeletal defect might underlie these abnormalities, and a cytoskeleton-dependent function, the surface distribution and mobility of concanavalin-A receptors, was studied on neutrophils from Schwachman's syndrome patients. Approximately a third of the neutrophils in each patient showed a patched distribution of fluorescein-conjugated concanavalin A (FITC-con A) rather than the usual diffuse staining pattern. These patched neutrophils also bound larger amounts of FITC-con A than diffusely stained or capped PMN from the same patient. Antitubulin treatment did not alter the proportion of patched PMN. These findings suggest that a cytoskeletal defect underlies the patching of FITC-con A on the PMN surface. This defect could also contribute to the abnormal chemotaxis and frequent infections found in Shwachman's syndrome patients.