Expression of T Cell Receptor Associated Proteins During Human T Cell Development

Abstract

T cells express membrane T cell receptor (TCR) heterodimers (TCRαβ or TCRτδ) which are associated with a set of monomorphic proteins recognized by CD3 monoclonal antibodies (MAbs). When CD3 MAbs are applied to suspensions of unpermeabilized infant thymocytes 50%–75% of cells are heterogeneously labeled (Lanier et al., 1986): approximately 50% of these are weakly positive (CD3^dim) and 50% are strongly CD3⁺ (CDS^bright; Fig. 1). The remaining cells do not show membrane CD3 (mCD3) expression. However >90% of these mCD3 cells exhibit CD3ε and CD3δ molecules in the perinuclear area when the samples are reinvestigated in cytocentrifuge preparations (Furley et al., 1986; Campana et al., 1987). The mCD3.cytoplasmic CD3 (cCD3)⁺ thymocytes include the highly dividing immature large blasts strongly terminal deoxynucleotidyl transferase positive (TdT⁺), CD7⁺, and heterogeneously CD2⁺ and CD5⁺ (Bradstock et al., 1980; Campana and Janossy, 1988).