title: Semi-quantitative determination of IgG-binding structures on bacteria by direct fluorescence technique.
abstract: A simple semiquantitative method for determination of IgG-binding structures on bacteria by direct fluorescence technique is described. The fluorescence of bacterial bound IgG-FITC-conjugate was measured in a paste-like bacterial sediment by using a fluorescence microscope photometer unit. For this purpose sharply centrifuged IgG-FITC conjugate treated bacteria, from which the washing fluid was carefully removed, were transferred to a glass slide and fluorescence was measured at the contact layer of the adhered drop on the inverted slide. The measured fluorescence intensity area was found to be correlated with the amount of bound IgG-FITC/cell, if bacteria had been incubated with an excess of fluorescein labeled IgG. The IgG-binding of different streptococcal strains was compared with the average IgG-binding of strain Cowan I resulting from 13 different cultivations. For strain Cowan I 9.4 X 10(4) IgG-molecules were estimated to bind on one staphylococcal cell. For a screening of IgG-binding bacterial strains the method did not demand a standardization of bacteria by cell counting.
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D007074:Immunoglobulin G / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D013211:Staphylococcus aureus / Q000378:metabolism*
chemical_list: D007074:Immunoglobulin G