Ultrastructural localization of cationic proteins in human polymorphonuclear leukocytes.

The present investigation is concerned with the use of the post-formalin ammoniacal silver reaction to detect the arginine-rich cationic proteins in human polymorphonuclear leukocytes at the ultrastructural level. These proteins appear to function as neutral proteases in antibacterial action and as mediators of inflammation. Originally, the ammoniacal silver reaction relied upon primary fixation in dilute formalin which prevented optimum fixation of tissues. This study shows that by using the proper sequence of glutaraldehyde fixation and the ammoniacal silver solution in conjunction with osmium tetroxide treatment, better fixation of the tissue and localization of the ammoniacal silver reaction can be achieved. Also, the ammoniacal silver reaction in human polymorphonuclear leukocytes is exclusively located in the large, crystalline cytoplasmic granules of eosiniphils. All other cytoplasmic granules of neutrophils, eosinophils, and basophils were found to be devoid of the ammoniacal silver reaction product. These results are contrary to previously published experimental data. Possible explanations for this discrepancy are discussed.