Turkey beta 2-microglobulin--II. Physiological parameters investigated by radioimmunoassay

A competitive binding radioimmunoassay (RIA) was developed utilizing 125I-labeled turkey beta 2-microglobulin (beta 2m), rabbit anti-turkey beta 2m serum and polyethylene glycol for separation of bound and free antigen. The antibody-antigen reaction was demonstrated to be monospecific by immunofixation electrophoresis. Characteristic parameters of the RIA were: nonspecific binding, 5.5%; linear dose-response range, 0.24-64.0 ng turkey beta 2m; dose-response correlation coefficient, -0.995; assay sensitivity, 0.52 ng; upper limit of precision, 40.4 ng. RIA analysis of adult turkey tissue and organ homogenates revealed highest amounts (greater than 10 micrograms turkey beta 2m/g) in liver and kidney and intermediate levels (2-10 micrograms/g) in lymphoid organ (thymus, spleen, caecal tonsil, bursa), skin and lung extracts. Erythrocytes and peripheral blood lymphocyte extracts contained 8.0 and 5.1 micrograms/10(9) cells respectively whereas all other tissues examined expressed greater than 2.0 micrograms/g. The beta 2m content in turkey serum was 192.5 micrograms/ml. The molecular weight distribution of turkey beta 2m in serum determined by gel permeation chromatography consisted of a minor component of approximately 60,000 daltons and a major fraction eluting at a position characteristic of free beta 2m. A cross-reaction between turkey and mammalian beta 2ms was not observed.