Dear Collegues: there was some discussion on phagocytosis that I would like to comment. 1. The important principle is to use whole blood. Ficoll disturbs the test and cultered cells are much slower. 2. The next is to freeze the result and lyse. 3. Quenching is done well with FITC labeled organisms. 4. Cell aggregates should be avoided as the quenching dye doesn´t reach the target. 5. The pH dependent flurescence intensity of fluorescein does not seem to play a major role (acidification in the phagosome) because BODIPY (pH independent) stained E.coli give the same time course. 6. The bacteria should be clean (no debris), of similar size (small CV), sterile (no other bacteria), fixed without disturbing the surface and occur as singlets. 7. Opsonization is done by the plasma in the whole blood unless you are dealing with immunodeficient patients or little children. Preopsonized bacteria test the phagocytosis more directly independent of the patients specific Ig and complement levels. 8. E.coli is opsonized more by complement, S. aureus more by immunoglobulin. 9. Consider the different principles at various size ranges: Immune complexes, bacteria, yeast and tumor cells. These were some of the points we considered when I developed the test at ORPEGEN years ago for clinical studies in immunopharmacology. A good day to day reproducibility over long times was a prerequisite for clinical trials and requires a serious batch control. We also used it for animal studies and I know from collegues that it works well for pigs, rabbits, rats and mice. Those who have further questions may contact me directly as we have no internet access at our hospital or Werner Hirt at ORPEGEN (via the purdue site). Thomas Nebe Klinikum Mannheim Faculty for Clinical Medicine, Univ. of Heidelberg Inst. f. Clinical Chemistry Theodor-Kutzer-Ufer 1-3 D-68167 Mannheim, GERMANY Phone: +49 621 383-3485 FAX: +49 621 383-3819
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