Class II-restricted IgG2ab-specific T cells recognize a signal-minus form of the V-CH3b antigen.
To study the question when and where self peptides become associated with major histocompatibility complex class II molecules for tolerance induction, we recently developed a system in which the intracellular site(s) of antigen expression could be manipulated using gene cloning techniques. We previously constructed a truncated IgGa gene comprising a variable (V) domain and the CH3 domain (not including the membrane exons) from the IgG2ab heavy (H) chain. The secreted form of the V-CH3b protein was expressed at high levels under control of the Ig H chain enhancer in Ia+ B lymphoma cells and was efficiently recognized by class II-restricted IgG2ab-specific T cell hybrids. Here we describe a modified V-CH3b gene construct in which the sequences encoding the signal peptide were deleted. A strong argument can be made that the signal-less V-CH3b protein is predominantly expressed in the cytosol. We show that transfected L cell lines expressing the signal-less form of the V-CH3b protein can stimulate class II-restricted IgG2ab-specific T cells. Cell mixing experiments indicate that this response cannot be due to passive uptake of soluble antigenic peptides released into culture supernatants. These experiments demonstrate that a cytoplasmic protein having no obvious means of reaching the cell surface can be presented to class II-restricted T cells.
Bikoff
E K
EK
Department of Obstetrics, Gynecology, and Reproductive Sciences, Mount Sinai School of Medicine, New York, NY 10029.
D000818:Animals; D000941:Antigens / Q000032:analysis* / Q000235:genetics; D005803:Genes, Immunoglobulin; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D007127:Immunoglobulin Constant Regions / Q000235:genetics; D007074:Immunoglobulin G / Q000235:genetics / Q000276:immunology*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics; D007739:L Cells / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D013601:T-Lymphocytes / Q000276:immunology*; D014162:Transfection
D000941:Antigens; D000949:Histocompatibility Antigens Class II; D007127:Immunoglobulin Constant Regions; D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region