Reversed passive arthus reaction using horseradish peroxidase as antigen. I. Light microscopical observations

The localization of immune complexes in epidermis and upper dermis: electron microscopic studies on reversed passive Arthus reaction

A reversed passive Arthus reaction was induced in guinea pigs using horseradish peroxidase as antigen. An electron microscopic study on the cutaneous localization of the immune complexes was performed applying a peroxidase reaction. Precipitates of immune complexes were found within the walls of small blood vessels and among the collagen bundles in the dermis. The adherence of immune complexes to numerous eosinophils was observed and some of immune complexes were phagocytosed by neutrophils. The adherence of immune complexes to fibroblasts and the deposits of immune complexes in some areas of the basement membrane zone, especially in the zona diffusa, were found in the upper dermis and in the papillae. In the lower layers of the epidermis, we observed immune complexes adhering to the cell membranes of keratinocytes.

Transient immune deposits in the papillary dermis and in the epidermis. A light-microscopical study on the experimental Arthus reaction

To have as further insight into the localizations of immune deposits in the skin the reversed passive and the passive Arthus reactions were carried out in the foot-pads skin of guinea-pigs using horseradish peroxidase as antigen. The transient localizations of immune deposits in the papillary dermis and in the epidermal cell layer were observed in the skin of the reversed passive Arthus reaction, but not in the skin of the passive Arthus reaction. Following the immune deposits in the papillae including the capillary walls and the dermoepidermal junction, the papillary dermis became widened, swollen, and edematous, being infiltrated by PMN's. In the epidermal layer, the immune deposits were found as fine granular aggregates adhering to the epidermal cells or to the dendritic cells. Although the immune deposits disappeared promptly from the papillae and the inflammatory reactions were slightly and transient, the epidermal cell layer became thickened, and several mitotic figures of the epidermal cells were observed.

Ultrastructural evidence for lack of tissue damage in a local immune complex reaction: a study of a mild passive Arthus reaction

An electron microscopic study of a mild reversed passive Arthus reaction (RPAR) was performed using a horeradish peroxidase (HRP)-anti-HRP system to demonstrate the biological usefulness of the process which exists to clear tissue of immune complexes. To disclose the antigen, HRP, the biopsy material was subjected to a peroxidase reaction. HRP was mainly detected within irregular electron-dense precipitates which were considered insoluable HRP-anti-HRP immune complexes. Neutrophils were found to phagocytose and digest the deposited immune complexes in a similar way as described previously. But there was no vascular and other tissue damage. This study provides morphological evidence that the process of clearing tissues of immune complexes need not be harmful to the host.