Summary. A sensitive radiolabelled anti‐antiglobulin method was devised and applied to quantitating red blood cell‐bound C3d (RBC‐C3d) in samples from 174 normal blood donors. C3d was demonstrable on all RBC examined; 98% of values fell over a broad range, with the highest values being approximately 3·5 × the lowest values (equivalent to 50–160 molecules of C3d per cell). RBC‐C3d did not correlate with sex or age (over 18–65 years); indirect evidence suggests that values for the paediatric age group will fall in the same normal range. Studies on samples obtained weekly for 10–12 weeks from six adult males and six adult females indicated stable levels of RBC‐C3d for individual subjects; i.e. high normals, mid normals and low normals remained in their characteristic range levels over the period of observation. For comparison, RBC‐C3d was measured in samples from 313 randomly selected hospitalized adult patients. 33% of the values were above the normal range; 8% were elevated to a level likely to have been detectable by a direct anti‐C3d antiglobulin test. The great majority of elevated values occurred in patients not ordinarily considered to have autoimmune conditions. The results provide background for studies of the aetiology and significance of RBC‐C3d in health and disease.
The investigation explored whether weak positive or "rough" direct antiglobulin test (DAT) reactions observed with commercial polyspecific reagents could be correlated with the amount of C3d bound to normal donor red blood cells (RBC). Employing a radiolabeled anti-antiglobulin method, RBC-bound C3d was measured on 101 normal donor samples. In a second phase of the study, RBC-bound C3d plus igG were measured on an additional 141 donor samples. In neither phase of the study was a correlation observed between weak positive antiglobulin reactions and the amount of RBC-bound serum globulins.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.