Mercury-induced autoreactive anti-class II T cell line protects from experimental autoimmune encephalomyelitis by the bias of CD8+ antiergotypic cells in Lewis rats.
Brown-Norway (BN) rats injected with HgCl2 develop a systemic autoimmune disease associated with a polyclonal B cell activation, due to autoreactive T cells specific for self-class II molecules, while Lewis (LEW) rats injected with HgCl2 do not exhibit autoimmunity and develop a non-antigen-specific, CD8-mediated immunosuppression assessed by a depression of T cell functions, and a protection against experimental autoimmune encephalomyelitis (EAE). Resistance to HgCl2-induced autoimmunity is not due to these suppressor cells since treatment with an anti-CD8 monoclonal antibody (mAb) did not allow autoimmunity to appear. The absence of autoimmunity in this strain could result from the absence of autoreactive T cells, or from quantitative or qualitative differences of these cells between susceptible and resistant strains. In the present study, we show that CD4+ anti-class II T cells are present in HgCl2-injected LEW rats and are as frequent as in BN rats when assessed by limiting dilution analysis. LEW CD4+ autoreactive T cell lines were derived. They proliferated in the presence of normal class II-bearing cells, secreted interleukin 2, and did not induce B cells to produce immunoglobulins. Transfer of one of these lines, LEW Hg A, into normal LEW rats led to the appearance of CD8+ cells responsible for a non-antigen-specific immunosuppression that induced complete protection from EAE. Immunosuppression was abrogated after treatment with an anti-CD8 mAb. In vitro, CD8+ cells from rats injected with the LEW Hg A T cell line proliferated in the presence of activated T cells whatever their origin. We conclude that HgCl2 induces CD4+ autoreactive T cells that proliferate in the presence of class II+ cells in susceptible BN as well as in resistant LEW rats. But while these cells collaborate with B cells to produce autoantibodies in BN rats, they initiate in LEW rats a suppressor circuit involving antiergotypic CD8+ suppressor cells.
Castedo
M
M
INSERM U28, Hôpital Broussais, Paris, France.
Pelletier
L
L
Rossert
J
J
Pasquier
R
R
Villarroya
H
H
Druet
P
P
D000818:Animals; D001327:Autoimmune Diseases / Q000139:chemically induced / Q000276:immunology* / Q000517:prevention & control; D001402:B-Lymphocytes / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D016827:CD8 Antigens; D002455:Cell Division; D002478:Cells, Cultured; D004660:Encephalitis / Q000139:chemically induced / Q000276:immunology* / Q000517:prevention & control; D005260:Female; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D008297:Male; D008627:Mercuric Chloride; D051381:Rats; D011917:Rats, Inbred Lew; D013601:T-Lymphocytes / Q000276:immunology* / Q000637:transplantation; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000276:immunology
D016827:CD8 Antigens; D000949:Histocompatibility Antigens Class II; D008627:Mercuric Chloride