Changes in the expression of several neutrophil antigens occurred throughout a 10-day course of G-CSF Most of the changes occurred after one dose, but additional changes occurred later in the 10-day course and after its completion. These changes may affect the function of G-CSF-mobilized granulocytes.

NB1 specificity is made up of at least two separate epitopes. The expression of NB1 varied among antigen-positive individuals. While NB1 is expressed by a 56- to 64-kDa glycoprotein, the structure of this protein on antigen-negative cells has not been determined.

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.

The neutrophil-specific NB antigen system has been serologically characterized with human alloantisera. Two alleles, NB1 and NB2, have been described. NB1 is expressed on a subpopulation of peripheral blood neutrophils in 97 percent of healthy donors. Human alloantibodies have been used to identify the 58- to 64-kDa glycoprotein (GP) on which NB1 is located. NB1 can usually be detected by both a granulocyte immunofluorescence (GIF) assay and a granulocyte agglutination (GA) assay, but neutrophils from some donors have been found to react with anti-NB1 in GIF but not in GA assays. To determine if the latter neutrophils express NB1 and the corresponding 58- to 64-kDa GP, these neutrophils were probed with rabbit and human sera specific for NB1. First, the proportion of neutrophils that express NB1 was quantitated. Neutrophils from donors that typed as NB1-positive in both GA and GIF assays were analyzed by flow cytometry with antisera to NB1. Human and rabbit anti-NB1 reacted with 71 +/- 17 percent and 70 +/- 17 percent of neutrophils, respectively. There was no difference in the expression of NB1 in NB1-homozygous and NB1-heterozygous individuals. In contrast, significantly fewer neutrophils from four donors that typed as NB1-positive in GIF assay but not GA assay reacted with human (27 +/- 12%; p < 0.001) and rabbit (26 +/- 12%; p < 0.001) anti-NB1. When neutrophils from these same four donors were probed with rabbit and human anti-NB1 by immunoblotting and immunoprecipitation, the 58- to 64-kDa GP was identified.(ABSTRACT TRUNCATED AT 250 WORDS)

We have previously described a 24-year-old woman with quinine-dependent antibodies that reacted with neutrophils, red blood cells (RBCs), platelets, and T lymphocytes. The drug-dependent neutrophil antibody was found to react with 85- and 60-Kd neutrophil membrane molecules. In these studies, we further characterized these molecules and found that both were glycosyl-phosphatidylinositol (GPI)-linked and contained sialic acid residues and N-linked carbohydrate side chains, but neither contained O-linked carbohydrates. The protein backbone of the 60-Kd molecule was 45 Kd, and the 85 Kd glycoprotein (GP) was made up of 33- and 31-Kd proteins. While some GPI-anchored neutrophil GPs are released by stimulated neutrophils, neither the 85- nor the 60-Kd GP was released by neutrophil stimulated with C5a, f-met-leu-phe (FMLP), or phorbol myristate acetate (PMA). Neutrophil-specific antigen NB1 is located on a 58- to 64-Kd GP. To determine if the quinine-dependent antibody and anti-NB1 recognize the same GP, immunoprecipitation studies were performed with the quinine-dependent antibody using neutrophils with varying NB1 phenotypes. The 60-Kd GP was detected on NB1-positive neutrophils from 11 of 12 donors tested, but not on NB1- negative neutrophils from two donors tested. After solubilized 125I- labeled neutrophils were absorbed with anti-NB1, the quinine-dependent antibody immunoprecipitated the 85-Kd GP, but not the 60-Kd GP. These results indicate that anti-NB1 and the quinine-dependent antibody identified the same GP. The 85-Kd GP was detected on neutrophils from all 14 donors tested. The electrophoretic mobility of the 85-Kd GP was similar to the electrophoretic mobility of the major 125I-labeled neutrophil protein.