TCR-alpha chain-like molecule is involved in the mechanism of antigen-non-specific suppression of a ubiquitin-like protein.
Although existence of suppressor T cells is a controversial issue in cellular immunology, several lines of evidence indicate that T-cell-receptor alpha-chain (TCR-alpha) is a critical component of suppressor factors produced by these cells. Monoclonal non-specific suppressor factor (MNSF), a lymphokine produced by murine T-cell hybridoma, possesses pleiotrophic antigen-non-specific suppressive functions. Recently, we have shown that the 70,000-MW MNSF comprises an 8000-MW ubiquitin-like polypeptide and other subunit(s). Here we report that the 8000-MW ubiquitin homologue is associated with an intracellular TCR-alpha (but not TCR-beta)-like molecule and released from the cells. The affinity eluates obtained from the culture supernatants of E17 cells and concanavalin A (Con A)-activated splenocytes with anti-TCR-alpha monoclonal antibody (mAb) showed an antigen-non-specific, major histocompatibility complex (MHC)-non-restricted suppression. Immunoblot analysis demonstrated that anti-TCR-alpha, but not anti-TCR-beta, mAb recognizes native 70,000-MW MNSF. In addition, we found the dissociation of the 8000-MW polypeptide from the 62,000-MW TCR-alpha cross-reactive protein by hydrolase which cleaves isopeptide bonds. Thus the covalent attachment of ubiquitin-like protein(s) may be involved in the underlying mechanism of suppressor T-cells and TCR-alpha-like molecule(s) might be a main link between antigen-specific and non-specific suppression.
Nakamura
M
M
Department of Biochemistry, Shimane Medical University, Izumo, Japan.
Tsunematsu
T
T
Tanigawa
Y
Y
D000818:Animals; D019759:Carbon-Nitrogen Lyases / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D018929:Cell Culture Techniques; D003208:Concanavalin A / Q000276:immunology; D005260:Female; D007108:Immune Tolerance; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008970:Molecular Weight; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology*; D013154:Spleen / Q000201:enzymology / Q000276:immunology; D013491:Suppressor Factors, Immunologic / Q000737:chemistry / Q000276:immunology; D014452:Ubiquitins / Q000276:immunology*
D016693:Receptors, Antigen, T-Cell, alpha-beta; D013491:Suppressor Factors, Immunologic; D014452:Ubiquitins; D003208:Concanavalin A; D019759:Carbon-Nitrogen Lyases; C034300:isopeptidase