Conjugates of Immunoglobulin G with Different Fluorochromes

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Abstract
Conjugate fractions of IgG labelled with FITC, MRITC, RB200SC or RBITC were tested on different substrates and the resulting fluorescence was evaluated with the Ploem optical system. Immunofluorescence sensitivity was characterized by the end point of specific staining. Conjugate quality was further defined by a specificity interval factor. Non‐specific staining end points exhibited an inverse semi‐logarithmic correlation with the molar FITC/protein ratio, while the influence of this ratio on specific staining varied greatly between different conjugates. Best sensitivity, combined with a favourable specificity interval, was obtained for selected fractions of MRITC and RB200SC conjugates. An inconsistent tendency of such conjugate fractions to produce non‐specific background staining was reduced by bovine serum albumin or by tissue powder adsorption. Several substrates were evaluated with regard to their usefulness in performance testing Carried out to determine the immunological specificity of conjugates. Reliable evidence of binding specificity was obtained by applying the conjugate absorbed in excess with the corresponding soluble antigen.