Cell labeling and sorting by rosette formation. Use of biotin-avidin binding.

The binding of biotin by avidin has proven to be a useful adjunct to antigen-antibody reactions in a number of immunological labeling systems. This work has applied it to rosette formation, for identification and separation of selected lymphocytes. Three procedures were compared which incorporated the biotin-avidin reaction into a model system for the rosetting of murine T lymphocytes. The reaction was most effective in conjunction with antibodies binding to the red cell, instead of using red cells which were biotinated on endogenous cell surface proteins. Physical separation of these rosettes from unrosetted cells was demonstrated with magnetic filtration, in a preliminary experiment. One interpretation of differences in effectiveness of rosette formation in the three systems tested is in terms of the flexibility of the antibody molecule, as compared with avidin. The principal finding was that, if employed in a multiple-stage 'sandwich' labeling system, avidinbiotin binding was fully effective and provided new versatility in the design of such rosetting schemes.