Quantification of ultrastructural variations in enriched blood basophils: correlation of morphological changes and antigen-induced histamine release.

Highly purified preparations of human basophils have been studied ultrastructurally to delineate quantifiably those alterations associated with immunologically-induced histamine release. Of six characteristic variations of basophil morphology, totally degranulated cells, those with some exteriorized granules and those with some extracellular vesicles were almost exclusively associated with antigen challenge. Of these, total degranulation without extracellular granules or vesicles was most frequent. A correlation was found between percentage histamine released and percentage totally degranulated cells present in the samples incubated with antigen. In addition, increased plasma membrane folding and irregularity were more prevalent in stimulated samples than in controls and their mean frequency was related quantifiably to the percentage of histamine released in each group. Cells with empty vesicles or electronlucent intracellular granules or both occurred to the same extent in experimental and control aliquots. The possible of histamine release is discussed.