Cutaneous deposition of immune complexes in chronic serum sickness of mice induced with cationized or unaltered antigen.

We have previously shown that cationic proteins localize to the dermal-epidermal junction (DEJ) after i.v. injection in experimental animals. In the present studies, cationized rabbit IgG was used as antigen for induction of chronic serum sickness in C57BL/6J mice over a period of 4 weeks. The formation of immune deposits was examined by immunofluorescence microscopy at weekly intervals during chronic antigen administration and at 7 weeks from the initiation of studies. Chronic administration of the cationized antigen led to immune complex deposits at the DEJ, while administration of the same antigen in native form did not lead to these deposits. Junctional immune deposits increased with higher doses of cationized antigen and paralleled renal extraglomular deposition in intensity, persistence, and morphology. Mice given cationized antigen also demonstrated vascular immune complex deposits without complement, while mice given native antigen had complement deposits and developed perivascular inflammation. No inflammation or complement deposition was detected at the DEJ in either group. Charge properties of circulating antigens are important in determining tissue sites of immune complex deposition and inflammation. Circulating cationic antigens can lead to immune deposits at the DEJ.