Historically, T and B lymphocytes have been identified and
enumerated using cell markers such as the sheep erythrocyte
receptor on T lymphocytes (E-rosette) and surface membrane
(Sm) Ig on B lymphocytes.
Although specific for T
lymphocytes, E-rosette methodology is limited in that it
provides for visual identification and manual enumeration of
sheep erythrocyte - T lymphocyte complexes by light
microscopy only. Measurement of SmIg for identification and
enumeration of B lymphocytes is also limited in that other
cellular populations may express SmIg and/or bind Ig via
receptors for the Fc portion of IgG resulting in false Ig positivity.