IgM are associated to Sp alpha (CD5 antigen-like).
In 1993, we reported the presence of an IgM-associated peptide (M(r) 44 kDa; pI 5.45) in all immunoglobulin M (IgM) fractions purified from plasma/serum by various methods. This peptide was absent in Ig fractions of non-IgM isotypes. The N-terminal sequence was determined as being APPSGVRLVGGLH. To gain insight into the nature of this peptide, we further analyzed, using modern proteomic tools, the IgM-associated peptide isolated from cryoglobulins. Mass spectrometry revealed three peptides of different masses: 2203.13 (ELGCGAASGTPSGILYEPPAEK), 1564.83 (KPIWLSQMSCSGR), and 1544.77 (EATLQDCPSGPWGK). Theses sequences together with the already known N-terminal sequence allowed us to identity the IgM-associated peptide as Sp alpha (O43866 in TrEMBL database; CD5 antigen-like). Sp alpha is a member of the scavenger receptor cysteine-rich superfamily of proteins. This family includes the T-and B-cell antigens CD5 and CD6, and several of its members influence immune cell fate. Our finding may have important implications in the understanding of the homeostasis of IgM antibodies.
Tissot
Jean-Daniel
JD
Service Régional Vaudois de Transfusion Sanguine, Lausanne, Switzerland. jean-daniel.tissot@chuv.hospvd.ch
Sanchez
Jean-Charles
JC
Vuadens
Françoise
F
Scherl
Alexander
A
Schifferli
Jürg A
JA
Hochstrasser
Denis F
DF
Schneider
Philippe
P
Duchosal
Michel A
MA
D000595:Amino Acid Sequence; D018956:CD5 Antigens / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D007075:Immunoglobulin M / Q000737:chemistry / Q000378:metabolism*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data
D018956:CD5 Antigens; D007075:Immunoglobulin M