Erythrocyte rosettes provide an analogue for Schiff base formation in specific T cell activation.
Human T cells spontaneously bind sheep E and this reflects physiologic interactions between specific adhesion molecules, principally T cell CD2, and the sheep equivalent of LFA-3. This interaction is important in T cell adhesion and in transmission of accessory activational signals. In this respect, E rosettes provide a partial analogue for T cell:accessory cell interaction and rosetting induces functional alterations in T cells. In studies of Ag-dependent T cell activation, we have obtained evidence that the formation of covalent Schiff bases between ligands on APC and T cell is an essential element. In our study, the specific chemical criteria defining Schiff base formation were applied to T cell E rosettes formed at room temperature, as follows: 1) Prior formation of Schiff bases on T cell epsilon-amino groups by glutaraldehyde inhibited E rosette formation. 2) Rosette formation was inhibited in the presence of exogenous lysine. 3) Reduction of constitutive T cell aldehydes by NaBH4 inhibited subsequent E rosette formation. In response to these chemical modifications of cellular ligands, T cell E rosette formation and T cell inductive interaction with APC were affected in the same way. 4) Oxidation of NaBH4-treated T cells by NaIO4 or galactose oxidase to regenerate cell-surface aldehydes on N-acetylneuraminic acid or galactose residues respectively, consistently restored E rosette formation. 5) Conversion of reversible Schiff bases to irreversible secondary amines by NaCNBH3 stabilized E rosettes against mechanical disruption. Together, these data demonstrate that E rosettes provide an analogue for the Schiff base-forming reactions that are essential in specific T cell activation.
Rhodes
J
J
Department of Experimental Immunobiology, Wellcome Biotech, Beckenham, Kent, U.K.
D000818:Animals; D000938:Antigen-Presenting Cells / Q000502:physiology; D001894:Borohydrides; D004910:Erythrocyte Membrane / Q000276:immunology; D006801:Humans; D019811:Hydroxylamine; D006898:Hydroxylamines; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D010084:Oxidation-Reduction; D012397:Rosette Formation; D012545:Schiff Bases; D012756:Sheep; D013601:T-Lymphocytes / Q000502:physiology*
D001894:Borohydrides; D006898:Hydroxylamines; D012545:Schiff Bases; D019811:Hydroxylamine