Immunofluorescence: a sensitive and rapid method for the detection of purine nucleoside phosphorylase in single cells

Indirect immunofluorescence was used as a rapid, sensitive and specific method for the visualization of the enzyme purine nucleoside phosphorylase in single cells. The enzyme was localized throughout cytoplasm of human lymphoblasts and fibroblasts but not in cell nuclei. This method is valuable for the detection of mutant enzyme protein in cell-mediated immunodeficiencies caused by purine nucleoside phosphorylase deficiency since it does not rely on enzyme activity. It requires only a limited number of cells and can therefore be used for the rapid screening for the presence of cross-reactive protein in immunodeficiency diseases.