Quantitative ultramicro-scale immunoenzymic method for measuring Ig antigenic determinants in single cells.

The Fluoro Ultra Micro Enzyme Linked Immuno Assay (FUMELIA) allows one routinely and quantitatively to measure a few thousand antigenic determinants on single cells. Highly purified Escherichia coli beta-galactosidase has been coupled to specific antibodies. By use of the Parafilm microcuvette techniuqe, the activity of the antibody-conjugated beta-galactosidase is assayed with a conventional spectrophotofluorometer. Attempts were undertaken to sensitize FUMELIA even further, so as to be able to detect a very few antigenic sites. It seems that even in its present state of development FUMELIA is more sensitive for the quantitation of cell-associated antigens than are techniques in which radiolabeled reagents are used. The potential of FUMELIA is illustrated by the quantitative measurement of membrane-bound immunoglobulins on single lymphocytes. It could be shown that T-cells as well as C-cells can synthesize Ig antigenic determinants. Thus it seems likely that T-cell receptors will, after all, be found to be immunoglobulins.