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Biochemical characterization of recombinant and circulating human Spalpha
M R Sarrias1, O Padilla, Y Monreal
1Servei d'Immunologia, Institut Clínic d'Infeccions i Immunologia, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Hospital Clínic, Villaroel 170, 08036 Barcelona, Spain.
Tissue Antigens
|March 11, 2004
Summary
Human Spalpha, a scavenger receptor superfamily protein, is a serum protein that binds to immune cells and immunoglobulin M (IgM), suggesting a role in immune system regulation and IgM homeostasis.
Area of Science:
- Immunology
- Biochemistry
- Molecular Biology
Background:
- Human Spalpha is a soluble protein expressed by macrophages in lymphoid tissues.
- It belongs to the scavenger receptor cysteine-rich superfamily (SRCR-SF), a group that includes CD5 and CD6.
- Limited functional and structural information is available for Spalpha.
Purpose of the Study:
- To produce recombinant Spalpha (rSpalpha) for biochemical studies.
- To generate monoclonal antibodies against Spalpha.
- To investigate Spalpha's isoforms, serum abundance, and interactions with other proteins.
Main Methods:
- Utilized an episomal mammalian expression system (pCEP-Pu/HEK 293-EBNA) to produce rSpalpha.
- Generated and selected four monoclonal antibodies reactive to rSpalpha.
- Employed Western blot, immunoprecipitation, and ELISA for antibody characterization.
- Used affinity chromatography for protein isolation.
Main Results:
- Identified two Spalpha isoforms (38 and 40 kDa) due to varying sialic acid content.
- Determined Spalpha is an abundant serum protein (60 μg/ml), circulating with other serum proteins.
- Demonstrated Spalpha's ability to bind to monocytes and lymphocytes.
- Confirmed Spalpha's interaction with immunoglobulin M (IgM) through affinity chromatography.
Conclusions:
- Spalpha is a circulating protein involved in immune cell interactions.
- The data suggest Spalpha plays a role in the homeostasis of immunoglobulin M (IgM) antibodies.
- Further research into Spalpha's function in immune regulation is warranted.