Effect of CD4 engagement on CD4-T cell receptor complexes.
To detect the presence of CD4-T cell receptor (TCR) complexes, we previously developed a flow cytometric method for measuring singlet-singlet energy transfer on human T cells labeled with fluorescein isothiocyanate-conjugated anti-CD4 and tetramethylrhodamine isothiocyanate-conjugated anti-TCR. Using the same procedure, we have now studied changes in the expression of CD4, TCR, and CD4-TCR complexes following CD4 engagement. Ligation of the D3 domain with OKT4, or the D1 domain with anti-Leu3a, induced CD4 and TCR down-regulation, while ligation of the D1 domain with gp120 did not. OKT4 caused a transient decrease in CD4-TCR association over 1 hr at 37 degrees C, while anti-Leu3a caused a steady-state decrease. In contrast, gp120 decreased CD4-TCR association mainly at 0 degrees C, rather than at 37 degrees C. Such alteration in CD4-TCR assembly may underly anti-Leu3a- and gp120-mediated inhibition of T cell antigen recognition and account for the negative effect of CD4 ligation on TCR-triggered responses.
Chuck
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Department of Medicine, North Shore University Hospital, Cornell University Medical College, Manhasset, New York 11030.
Cantor
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D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015704:CD4 Antigens / Q000276:immunology* / Q000378:metabolism; D002460:Cell Line / Q000276:immunology; D016650:Fluorescein-5-isothiocyanate; D015699:HIV Envelope Protein gp120 / Q000494:pharmacology*; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000276:immunology* / Q000378:metabolism; D012235:Rhodamines; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000276:immunology
D000911:Antibodies, Monoclonal; D015704:CD4 Antigens; D015699:HIV Envelope Protein gp120; D008562:Membrane Glycoproteins; D011948:Receptors, Antigen, T-Cell; D012235:Rhodamines; C009434:tetramethylrhodamine isothiocyanate; D015759:Ionomycin; D016650:Fluorescein-5-isothiocyanate; D013755:Tetradecanoylphorbol Acetate