A quantitative ELISA for measuring red cell-bound immunoglobulins.

An ELISA was developed for quantitating red-cell-bound IgG and IgA and its feasibility assessed on 50 blood donations and 32 clinical specimens with raised cell-bound IgG. Test and quality control samples and immunoglobulin standards (in red-cell lysate buffer) were assayed together. Calibration curves were derived from the standards, test values being read off and related to cell count. The working range was around 5-70 ng/ml, the upper limit being indefinitely extendable by dilution with lysate buffer. Ranges of results (and medians) in molecules per red cell were < 26-240 (40) for IgG and < 29-94 ( < 29) for IgA in the donations with 240-62,700 (1,200) for IgG and < 29-4,500 (73) for IgA in the clinical specimens. The method which can be adapted for any cell-bound immunoprotein should be particularly valuable in investigating autoimmune haemolysis.