IgM are associated to Spα (CD5 antigen-like)

Abstract

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.

Purification of Two Different Immunoglobulins (Igs) from Olive Flounder Paralichthys olivaceus and Analysis of Lactococcus garvieae Antigens by the Igs

“…PMF analysis allowed us to identify groups (c), (a´) and (d) as IgM or IgM precursor. Similarly, comparison of our 2-DE results to previously reported 2-DE maps of emerald rockcod, brown trout Salmo trutta and human IgMs (Hordvik et al, 2002;Pucci et al, 2003;Tissot et al, 1994Tissot et al, , 2002 suggested that the spots found in group (b) and (b¢) represent the light chain of olive flounder IgM. In addition, the spots found in group (d) were thought to be m chain fragments of IgM induced by freezing, as previously seen in IgM cryoglobulin from human and hybrid bass (Tissot et al, 1994(Tissot et al, , 2002Nitzan et al, 2003).…”

“…Furthermore, PMF followed by NCBI database searching identified the heavy chains of Ig proteins as IgM or IgM precursor. Previously, 2-DE analysis was used to divide human IgM cryoglobulin (proteins precipitated from plasma or serum at low temperatures and resolubilized by warming) into 5 groups: m chain of IgM (pI 5.6 -6.4, 80 kDa), m chain fragments of IgM, SPa, J-chain and light chain (Tissot et al, 1994(Tissot et al, , 2002. On the other hand, degradation of IgM due to freezing shock was observed in hybrid bass (Morone saxatilis ¥ M. chrysops) by SDS-PAGE analysis (Nitzan et al, 2003).…”

Global proteomic profiling reveals altered proteomic signature in schizophrenia serum

“…This evidence supports the hypothesis that CD5L has a role in the immune system as well as in the interaction with IgM. 14 Tissot et al 14 also report that CD5L is associated with IgM; however, the interaction between the two proteins is not clear. This report is supported by our finding of high correlation between the two proteins.…”

Recent advances in blood‐related proteomics

“…Using 2-DE analyses and MS, we also recently identified a new peptide, called hSpa or CD5L [50]. This peptide was only found when IgM were present, like in cryoglobulins (Fig.…”