Reliable method for the simultaneous detection of cytoplasmic and surface CD3ε expression by murine lymphoid cells

During their development, T‐cell precursors (pre‐T cells) undergo a variety of changes with respect to their expression of specific surface proteins. Among the most critical of the surface markers acquired by developing T cells is the T‐cell receptor (TCR)/CD3 complex. Prior to the assembly and transport of complete TCR/CD3 multimeric complexes to the plasma membrane, the individual constituent subunits are expressed in the cytoplasm (ER‐Golgi). In order to study the expression of the T‐cell receptor TCR/CD3 complex during pre‐thymic T‐cell differentiation, we have developed a flow cytometric technique for the simultaneous detection of surface (sCD3ϵ) and cytoplasmic CD3ϵ (cCD3ϵ). This technique, which employs fixation in 1% paraformaldehyde and permeabilization with 1% saponin and 0.025% digitonin, features reliable internalization and low nonspecific binding of anti‐CD3ϵ in murine lymphoid cells, as well as tissue culture cell lines. The combination of saponin and digitonin treatment was also compatible with the staining of sCD3 and other lymphocyte surface antigens such as Thy1, CD4, CD8, B220, and IgM. In contrast, permeabilization of cells with the detergents Tween 20 and Triton X‐100 was shown to remove surface‐bound anti‐CD3ϵ. The present technique permitted the detection of discernible sCD3ϵ and cCD3ϵ double and single positive lymphocytes and may prove useful in defining bone marrow‐resident pre‐T cells. © 1994 Wiley‐Liss, Inc.