Autoreactive eosinophils associated with spontaneous autocytotoxicity in bronchial asthma

Allergic autocytotoxicity (ACT) assay is extensively investigated as an in vitro equivalent of oral ingestion challenge with food antigens among patients with food hypersensitivity. In direct ACT, food antigenic determinants interact directly with plasma cell membranes of sensitive individuals. Antibody-dependent ACT is also known as antibody-dependent-cell-mediated-cytotoxicity (ADCC) phenomenon, when food antigens combine with specific antibody through cell membranes Fc receptors among normal and sensitive individuals. Spontaneous ACT is a separate mechanism of white blood cells disintegration which does not require in vitro priming of the cells, neither by antigen or antibody. Spontaneous ACT occurs in some individuals as "background noise" in addition to direct and antibody-dependent ACT. The exact cellular nature of ACT phenomena are unknown at the present time with the exception that the common identifying factor for each of them is the disintegration and death of human white blood cells. Electron microscopy studies among four bronchial asthma patients with spontaneous ACT demonstrated eosinophils with atypical crystalloid cores and diffuse autolytic pattern of granular membranes. These ultrastructural characteristics are associated with new functional profiles of eosinophils expressed morphologically as natural killer and/or suicidal potency. At least two subpopulations of eosinophils are mediating ACT. The first subpopulation has normal ultrastructure observed in direct ACT and the second subpopulations has altered morphology of eosinophils granules described in spontaneous ACT. The natural killer-suicidal eosinophils presented in patient with spontaneous ACT illustrate a new pathway of cytodestructive mechanism in anaphylactic injury.