The mixed antiglobulin rosetting reaction (MARR) and the direct antiglobulin rosetting reaction (DARR): sensitive tests for demonstration of immunoglobulin-bearing B lymphocytes.

The technology of the mixed antiglobulin rosetting (MARR) and the direct antiglobulin rosetting reaction (DARR) is reviewed. These tests have been found to be more sensitive than the standard direct immunofluorescence (DIF) method for delineation of Ig-bearing B lymphocytes and to have practical advantages over DIF. Further, with these rosette tests, an important B lymphocyte population has been identified which is Ig-negative by DIF and functionally quite different from typical DIF-positive B lymphocytes but which expresses a low density of surface membrane Ig that is detectable by the MARR and the DARR.