2. Metabolic Enzyme/Protease Apoptosis
  3. Endogenous Metabolite Apoptosis
  4. Protein A

Protein A (SPA) is an immunoglobulin (Ig)-binding protein that exists on the bacterial surface and can be freely secreted into the extracellular environment. Protein A blocks opsonophagocytosis and induces B cell apoptosis in vitro by binding to the Fc region of antibodies and the Fab region of B cell receptors. Protein A can form toxic immune complexes with IgG, thereby inducing leukocyte necrosis. Protein A contributes to the virulence expression of Staphylococcus aureus. Protein A triggers allergic reactions in IgG-pretreated mouse models. Protein A can be used in studies related to immune system diseases.

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Protein A

Protein A Chemical Structure

CAS No. : 308083-69-4

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Protein A Related Antibodies

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Description

Protein A (SPA) is an immunoglobulin (Ig)-binding protein that exists on the bacterial surface and can be freely secreted into the extracellular environment. Protein A blocks opsonophagocytosis and induces B cell apoptosis in vitro by binding to the Fc region of antibodies and the Fab region of B cell receptors. Protein A can form toxic immune complexes with IgG, thereby inducing leukocyte necrosis. Protein A contributes to the virulence expression of Staphylococcus aureus. Protein A triggers allergic reactions in IgG-pretreated mouse models. Protein A can be used in studies related to immune system diseases[1][2][3].

In Vitro

Protein A (1 μM; 2 h) activates the human mantle cell VH3+ B-cell lymphoma MAVER-1 cells, increasing the CD69 expression level to 31.6% after 2 h of treatment, while the addition of fetal bovine serum inhibits this activation effect[1].
Protein A (1 μM; 5 min-16 h) exerts rapid toxicity on purified primary human B cells in medium supplemented with 10% human serum, causing an average 38% cell loss over incubation periods ranging from 5 min to 16 h[1].
Incubation of Protein A (1 μM; 5 min-2 h) with intact human IgG induces ≥90% cytotoxicity in the human mantle cell VH3+ B-cell lymphoma MAVER-1 cells, triggering rapid necrosis (90% of cells undergo necrosis within 5 min). This cytotoxicity is inhibited by immune sera from mice immunized with a non-binding SpA mutant[1].
At a concentration of 1 μM for 16 h in medium supplemented with 10% human serum, Protein A induces a 40% reduction in the total number of primary human leukocytes, including significant toxicity to CD19+ B cells and HLA-DR+ CD14+ monocytes, but exhibits no toxicity to HLA-DR+ CD14− dendritic cells[1].
Protein A reduces the phagocytic activity of phagocytes against *Staphylococcus aureus* via antibody chelation mediated by the Fc region, induces B cell apoptosis by binding to the B cell receptor through the Fab region, and eliminates the B cell population that produces *Staphylococcus aureus*-specific antibodies[2].

MedChemExpress (MCE) has not independently confirmed the accuracy of these methods. They are for reference only.

Protein A Related Antibodies

Cell Cytotoxicity Assay[1]

Cell Line: human mantle VH3+ B cell lymphoma cell line (MAVER-1)
Concentration: 1 μM
Incubation Time: 2 h
Result: Induced significant cellular toxicity, resulting in an average loss of ~75% of MAVER-1 B cells within 2 h in medium supplemented with 10% human serum.

Cell Cytotoxicity Assay[1]

Cell Line: human mantle VH3+ B cell lymphoma cell line (MAVER-1)
Concentration: 1 μM (in the presence of 500 nM human IgG, 2 μM human IgG Fab, 4 μM human IgG Fc, or 50 nM human IgM)
Incubation Time: 2 h
Result: Induced profound toxicity in the presence of 500 nM intact human IgG, with a mean 80% cell viability loss (≥90% toxicity observed in some replicates).
Showed no significant toxicity with 50 nM human IgM, 2 μM human IgG Fab alone, or 4 μM human IgG Fc alone.
Induced limited toxicity (median 10%) with an equimolar mix of Fab and Fc fragments.

Apoptosis Analysis[1]

Cell Line: human mantle VH3+ B cell lymphoma cell line (MAVER-1)
Concentration: 1 μM
Incubation Time: 5 min, 15 min, 30 min, 60 min
Result: Induced necrosis (90% of cells stained positive for LIVE/DEAD fixable dead-cell stain and negative for TUNEL staining) within 5 min when incubated with intact human IgG.
Maintained necrotic effect through 30 min, with 92% of cells staining as necrotic.
Decreased slightly to 72% necrotic cells by 60 min when incubated with intact human IgG.
Induced apoptosis (31% of cells stained TUNEL positive after 60 min) in the absence of human IgG.
In Vivo

Protein A (1 mg/23.8 pmol, i.v., single dose) induces allergic reactions in human IgG-pretreated VH3+ T15i knock-in transgenic mice and depletes up to 70% of peripheral VH3+ B cells[3].

MedChemExpress (MCE) has not independently confirmed the accuracy of these methods. They are for reference only.

Animal Model: Wild type C57BL/6 mice[3]
Dosage: 1 mg/23.8 pmol
Administration: i.v., single dose
Result: Induced allergic reactions in human IgG-pretreated VH3+ T15i knock-in transgenic mice and depleted up to 70% of peripheral VH3+ B cells.
CAS No.
Appearance

Liquid

Color

Colorless to light yellow

SMILES

[Protein A]
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Room temperature in continental US; may vary elsewhere.
Storage

Please store the product under the recommended conditions in the Certificate of Analysis.
Purity & Documentation

Purity: 93.27%

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COA (230 KB)

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Protein A Related Classifications

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Help & FAQs
  • Do most proteins show cross-species activity?

    Species cross-reactivity must be investigated individually for each product. Many human cytokines will produce a nice response in mouse cell lines, and many mouse proteins will show activity on human cells. Other proteins may have a lower specific activity when used in the opposite species.

Keywords:

Protein A308083-69-4SPAEndogenous MetaboliteApoptosisimmunoglobulin (Ig)-binding proteinapoptosisMAVER-1 cellsB cellsWild type C57BL/6 miceInhibitorinhibitorinhibit

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