Preferential expression of human Fc gamma RIIIPMN (CD16) in paroxysmal nocturnal hemoglobinuria. Discordant expression of glycosyl phosphatidylinositol-linked proteins.

Abstract

IntroductionThe isoform of FcyRIII (CD16) expressed on PMN has a GPI membrane anchor, and in paroxysmal nocturnal hemoglobinuria (PNH) there is a deficiency in Fc-yRIII expression on PMN. Contrary to expectation, however, CD16 expression is preserved (albeit at reduced levels) in all affected PNH PMN that completely lack the GPI-anchored proteins DAF (CD55) and CDS9.

NB1 mediates surface expression of the ANCA antigen proteinase 3 on human neutrophils

“…In addition, we had the opportunity to study neutrophils from a patient with PNH, an acquired clonal loss of GPI linker synthesis. 24 Our patient showed the expected reduction of CD66b and CD16b, and even loss of NB1 with a parallel lack of mPR3 expression on neutrophils. To provide firm evidence that NB1 expression confers the capability to express mPR3, we transfected different cell lines with NB1.…”

“…23 These patients show a variable decrease of GPI-linked proteins on their neutrophils. 24 In parallel to a healthy donor we document that the neutrophils of the patient with PNH had a major decrease in a number of GPI-linked proteins ( Figure 5C). No NB1 was detected on their surface, although intracellular NB1 was present in Western blot (data not shown).…”

On the interaction of IgG subclasses with the low affinity Fc gamma RIIa (CD32) on human monocytes, neutrophils, and platelets. Analysis of a functional polymorphism to human IgG2.

“…Platelets were then concentrated by centrifugation (7 min, 1,200 g) and three washes were performed with PBS/5 mM EDTA/0.5% FCS (26). PMN expressing reduced levels of FcyRIII were isolated from two patients with diagnosed paroxysmal nocturnal hemoglobinuria (PNH) (27,28). The neutrophil preparations from these patients contained -80% and -100% of (GPI-linked) FcyRIIIb deficient cells, respectively, and expressed -10% of normal Fc'YRIIIb levels.…”

“…Incubation of PMN with GPI-PLC, which resulted in removal of -90% of the GPI-linked FcyRIIIb, did not significantly affect the ability of these cells to bind hIgG2 (n = 3). hIgG2 dimer binding studies were, furthermore, performed with PMN isolated from two patients suffering from PNH, which is an acquired disorder resulting in strongly diminished expression of GPI-linked membrane proteins, such as FcyRIIIb (27,28). PMN of both these patients were found to express FcayRIIaHR only, and interacted weakly with hIgG2 dimers (resulting in 4 and 8% positive staining cells, respectively).…”

Paroxysmal Nocturnal Hemoglobinuria and Glycosyl Phosphatidylinositol Anchored Proteins That Regulate Complement

“…The extent of the deficiency varies greatly among patients (21,22). Further, the deficiency does not affect all GPI-linked proteins equally (23), and the extent of the deficiency varies among the different hematopoietic elements.…”