Immune complex detection by immunofluorescence on polymorphonuclear leucocytes : an experimental and clinicopathological study

Diseases, which are the result of immune reactions associated with tissue damage may be caused by several mechanisms. The immunologic mechanisms resulting in tissue damage have been categorized in 4 types (Gell and Coombs, 1968). 1. the anaphylactic type, mediated by IgE type of antibodies, resulting in immediate release of vasoactive arnines (e.g. histamine). 2. the cytotoxic type, mediated by IgG and IgM type of antibodies and resulting in phagocytosis of the target cells or lysis by complement activation. 3. the immune complex type, with either primary localisation of the immune complexes in the tissues (Arthus reaction) or circulating immune complexes with secondary tissue localisation. 4. the delayed type or cellular immune response mediated by thymus derived T-lymphocytes. In the studies to be reported, only diseases caused by the type 3 reaction, mediated by circulating immune complexes, are of concern. Examples of human diseases caused by the immune complex mediated type of tissue damage are a.o. serum sickness, systemic lupus erythematosus (SLE) and several types of glomerulonephritis

Flow cytometric determination of circulating immune complexes with the indirect granulocyte phagocytosis test

A method for the determination of circulating immune complexes (CIC) was adapted for flow cytometric analysis. Human granulocytes were used to phagocytose IgG-bearing CIC of serum from systemic lupus erythematosus (SLE) patients. A method for labeling the phagocytosed CIC with FITC-conjugated anti-human IgG was developed where the granulocytes remain in suspension during fixation and labeling. The fluorescence per cell, measured with a flow cytometer, is a measure of the total amount of the phagocytosed IgG. The results indicate that a rapid and quantitative method for the detection and measurement of phagocytosed CIC is possible using the flow cytometer