Characterization of the neutrophil molecules identified by quinine-dependent antibodies from two patients

Two patients with episodic pancytopenia and renal failure associated with quinine (Qn) ingestion were previously found to have Qn-dependent antibodies that reacted with red cells, platelets, and neutrophils. The purpose of these studies was to characterize the neutrophil antigens recognized by Qn-dependent antibodies from these two patients.

The neutrophil molecules recognized by the Qn-dependent antibodies in the sera from the two patients were analyzed by immunoprecipitation using 125I-labeled neutrophils. Neutrophils from 13 different donors were tested.

The Qn-dependent antibodies from Patient 1 immunoprecipitated a 60-kDa molecule on neutrophils from seven donors and an 85-kDa molecule on neutrophils from three donors. The Qn-dependent antibodies from Patient 2 reacted with a 32-kDa molecule on neutrophils from 5 donors, a 60-kDa molecule on neutrophils from 9 donors, and an 85-kDa molecule on neutrophils from 10 donors. Neutrophil-specific antigen NB1 is also located on a 60-kDa glycoprotein (GP). While the antibody in serum from Patient 1 did not show specificity for NB1, the antibody from Patient 2 detected the 60-kDa molecule on NB1-positive neutrophils from 9 of 11 donors tested and did not detect the 60-kDa molecule on NB1-negative neutrophils from 2 donors. In a monoclonal antibody immobilization of granulocyte antigens assay, the Qn-dependent antibody from both patients reacted with the 60-kDa molecule carrying NB1. The Qn-dependent antibody from a third patient, Patient 3, was previously found to react with an 85-kDa GP and the 60-kDa NB1 GP. To determine if the Qn-dependent antibodies from Patients 2 and 3 recognized the same 85-kDa GP, neutrophils were treated with serum from Patient 3 plus Qn to remove the 85-kDa GP. Then, serum from Patient 2 plus Qn no longer immunoprecipitated the 85-kDa GP.

The antigens recognized by Qn-dependent neutrophil antibodies were located on molecules of 85, 60, and 32 kDa. Qn-dependent antibodies from two patients reacted with the same 85-kDa GP and those from three patients reacted with the same 60-kDa GP. The 60-kDa molecule recognized by the Qn-dependent antibodies carried the NB1 antigen.