The RT6 rat lymphocyte alloantigen circulates in soluble form.
RT6 is a rat maturational lymphocyte alloantigen that appears to subserve important immunoregulatory functions. The lymphopenic diabetes-prone BioBreeding (BB)/Worcester rat is severely deficient in RT6+ T cells and develops spontaneous autoimmune diabetes mellitus. Transfusion of RT6+ T cells prevents the disease. Conversely, in vivo immune elimination of RT6+ T cells from the diabetes-resistant line of BB rats induces diabetes and thyroiditis. RT6 protein is expressed in two allotypic forms, each linked to the cell surface by a phosphatidylinositol (PI) anchor. The mechanism by which RT6+ T cells exert their regulatory function is not known, nor is the function of the RT6 protein defined. In this study, we investigated the possibility that, like other PI-linked proteins, RT6 also exists in a soluble form in the circulation. Using standard biochemical procedures we observed: (i) Soluble RT6 circulates in readily detectable amounts in all rat strains studied. (ii) The diabetes-prone BB rat circulates less RT6.1 than does any other strain, including the coisogenic diabetes-resistant line. (iii) Injections of monoclonal anti-RT6.1 antibody rapidly eliminate soluble RT6 from the circulation of diabetes resistant BB rats. The existence of a soluble form of a protein associated with immunoregulatory T cells suggests the possibility that soluble RT6 itself might possess immunomodulatory properties.
Waite
D J
DJ
Department of Medicine, University of Massachusetts Medical School, Worcester 01655.
Handler
E S
ES
Mordes
J P
JP
Rossini
A A
AA
Greiner
D L
DL
D036002:ADP Ribose Transferases; D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte; D015153:Blotting, Western; D006649:Histocompatibility Antigens / Q000737:chemistry / Q000276:immunology* / Q000302:isolation & purification; D007518:Isoantibodies / Q000494:pharmacology*; D008214:Lymphocytes / Q000276:immunology*; D008562:Membrane Glycoproteins; D051381:Rats; D011913:Rats, Inbred BB; D012995:Solubility
D000945:Antigens, Differentiation, T-Lymphocyte; D006649:Histocompatibility Antigens; D007518:Isoantibodies; D008562:Membrane Glycoproteins; C079330:RT6.1 antibody; D036002:ADP Ribose Transferases; C090163:Art2b protein, rat