IgM and IgG subclass distribution of human anti-Ro/SSA 60 kDa autoantibodies.
The Ro/SSA and La/SSB antigens are common targets for autoantibodies found in the sera of patients with Sjögren's syndrome and SLE. The anti-Ro/SSA and anti-La/SSB antibodies often appear together but are not cross-reactive. This paper describes the humoral autoimmune response to the Ro/SSA 60 kDa protein moiety with respect to the presence of IgM and IgG1-4 antibodies. IgM antibodies to the Ro 60 kDa protein coexisted with IgG anti-Ro 60 kDa antibodies in nearly half of the sera. A similar fraction also contained IgM anti-La/SSB antibodies. The frequency of sera with IgM antibodies of both specificities was that expected from random overlap. A predominating IgG1 anti-Ro 60 kDa response was found in all patients, but anti-Ro 60 kDa antibodies of the other IgG subclasses were present also in a high number of sera. This is in contrast to the reported IgG subclass distribution of anti-La/SSB antibodies. Mapping of IgM and IgG1-4 antibody recognition of different parts of the Ro 60 kDa protein was also performed. IgM and IgG1-4 antibodies of all sera reacted with the central part of the Ro 60 kDa protein, encompassing amino acid residues 181-320.
Wahren
M
M
Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden.
Ringertz
N R
NR
Pettersson
I
I
D001323:Autoantibodies / Q000097:blood*; D001324:Autoantigens / Q000276:immunology*; D006801:Humans; D015151:Immunoblotting; D007074:Immunoglobulin G / Q000097:blood*; D007075:Immunoglobulin M / Q000097:blood*; D020733:RNA, Small Cytoplasmic; D012216:Rheumatic Diseases / Q000276:immunology*; D012261:Ribonucleoproteins / Q000276:immunology*; D000097585:SS-B Antigen; D000099207:SS-A Antigen
D001323:Autoantibodies; D001324:Autoantigens; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins; D000097585:SS-B Antigen; D000099207:SS-A Antigen; C116006:RO60 protein, human