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CD4-T-cell antigen receptor complexes on human leukemia T cells
R S Chuck1, C R Cantor, D B Tse
1Department of Medicine, North Shore University Hospital-Cornell University Medical College, Manhasset, NY 11030.
Summary
CD4 and T-cell antigen receptor (TCR) form complexes on human T cells. This study developed a flow cytometry method to detect these CD4-TCR complexes, revealing their presence even without stimulation.
Area of Science:
- Immunology
- Cell Biology
- Biophysics
Background:
- CD4 and T-cell antigen receptor (TCR) comodulate on T cells upon antibody exposure.
- This comodulation suggests shared regulatory signals or physical association between CD4 and TCR.
- Understanding these molecular interactions is crucial for T-cell activation and signaling.
Purpose of the Study:
- To investigate the physical association of CD4 and TCR on the T-cell surface.
- To develop a method for detecting multimolecular assemblies on the plasma membrane.
- To determine if CD4 and TCR form stable complexes in the absence of external stimuli.
Main Methods:
- Development of a flow cytometry technique utilizing singlet-singlet energy transfer (SSET).
- Detection of energy transfer between fluorescein isothiocyanate (FITC)- and tetramethylrhodamine isothiocyanate (TRITC)-conjugated antibodies.
- Analysis of intact, single T cells (HPB-ALL leukemia cell line) to quantify CD4-TCR complexes.
Main Results:
- Successfully detected CD4-TCR complexes on the surface of HPB-ALL cells.
- Evidence suggests a stoichiometry of more than one CD4 molecule per TCR molecule.
- These complexes were present in the absence of stimulation and were not induced by the labeling antibodies.
Conclusions:
- CD4 and TCR exist as pre-formed complexes on the T-cell surface.
- The detected CD4-TCR complexes are stable and not in rapid equilibrium with free molecules.
- This finding provides direct evidence for physical association between CD4 and TCR, impacting T-cell signaling.