A Novel Leukocyte Adhesion Deficiency III Variant: Kindlin-3 Deficiency Results in Integrin and Nonintegrin-Related Defects in Different Steps of Leukocyte Adhesion

TLDR: The results suggest looking for a possible kindlin-3 involvement in membrane dynamical event independent of integrin-mediated adhesion in a patient with a new mutation of FERMT3 and lack of kindlins-3 expression in platelets and leukocytes.

Abstract: Leukocyte adhesion deficiency type III is a recently described condition involving a Glanzmann-type bleeding syndrome and leukocyte adhesion deficiency. This was ascribed to a defect of the FERMT3 gene resulting in abnormal expression of kindlin-3, a protein expressed in hematopoietic cells with a major role in the regulation of integrin activation. In this article, we describe a patient with a new mutation of FERMT3 and lack of kindlin-3 expression in platelets and leukocytes. We assayed quantitatively the first steps of kindlin-3–defective leukocyte adhesion, namely, initial bond formation, bond strengthening, and early spreading. Initial bond formation was readily stimulated with neutrophils stimulated by fMLF, and neutrophils and lymphocytes stimulated by a phorbol ester or Mn 2+ . In contrast, attachment strengthening was defective in the patient’s lymphocytes treated with PMA or Mn 2+ , or fMLF-stimulated neutrophils. However, attachment strengthening was normal in patient’s neutrophils treated with phorbol ester or Mn 2+ . In addition, the patient’s T lymphocytes displayed defective integrin-mediated spreading and a moderate but significant decrease of spreading on anti-CD3–coated surfaces. Patient’s neutrophils displayed a drastic alteration of integrin-mediated spreading after fMLF or PMA stimulation, whereas signaling-independent Mn 2+ allowed significant spreading. In conclusion, the consequences of kindlin-3 deficiency on β 2 integrin function depend on both cell type and the stimulus used for integrin activation. Our results suggest looking for a possible kindlin-3 involvement in membrane dynamical event independent of integrin-mediated adhesion.