Localization of lysosomal and peroxisomal enzymes in the specific granules of rat intestinal eosinophil leukocytes revealed by immunoelectron microscopic techniques.

Immunoelectron microscopic localization of lysosomal and peroxisomal enzymes in the eosinophil leukocytes of rat intestinal mucosa was studied by use of rabbit antibodies to the enzymes coupled to protein A-gold complex. Gold particle labeling for the lysosomal enzymes, beta-glucuronidase and cathepsin D, was present on specific granules, with a heavy concentration on their paracrystalline cores. The peroxisomal enzymes, acyl-CoA oxidase and catalase, were also found on these granules. The double labeling procedures using two different combination of anti-acyl-CoA oxidase and anti-beta-glucuronidase or anti-catalase and anti-cathepsin D revealed that these enzymes were simultaneously present in specific granules of the intestinal eosinophils. Quantitative analysis of the labeling on subcellular compartments confirmed that all enzymes examined are significantly localized within specific granules and that there is no significant labeling on other compartments such as the nucleus and cytoplasm. In the control sections incubated with an immunoglobulin G fraction from nonimmunized rabbits, no specific labeling was seen on the granules or other organelles. These findings indicate that enzymes which previously have been identified in some organs as lysosomal and in others as peroxisomal can be found together in eosinophil granules.