Rules-Based Medicine

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Granulocyte-Macrophage Colongy-Stimulating Factor (GM-CSF)

Ultrasensitive Immunoassay



Rules-Based Medicine’s (RBM) internally developed and manufactured ultrasensitive immunoassay to B Lymphocyte Chemoattractant (BLC, CXCL13) based on the Simoa® bead technology can accurately quantitate sub-pg/mL levels of BLC in human serum and plasma. Being able to accurately quantitate sub-pg/mL levels of BLC in human serum and plasma is valuable for pharmacodynamic analysis in the areas of autoimmune disease, oncology, infectious diseases, and organ transplant.


B lymphocyte chemoattractant [BLC, CXCL13, B-cell-attracting chemokine-1 (BAC-1)] belongs to the CXC chemokine family and is expressed in the liver, follicles of the spleen, lymph nodes, and Peyer’s patches by T follicular helper cells, dendritic cells, osteoclasts, and macrophages. BLC induces B cell chemotaxis by binding to the chemokine receptor, CXCR5. CXCL13/CXCR5 signaling also promotes progression and lymph node metastases of oral squamous cell carcinoma, hepatocellular carcinoma, renal cell carcinoma, neuroblastoma, leukemias, multiple myelomas, lymphomas, breast cancers, colorectal cancers, lung cancers, and prostate cancers. T cell-mediated rejection of kidney allografts has been linked to B cell clustering and more severe disease. CXCL13 serum levels have been identified as a potential biomarker for B cell clustering and was correlated with more severe disease. RBM’s Simoa BLC assay may be an important analytical tool for clinical studies of diseases involving B cell dysfunction.


Swiss-Prot Accession Number: O43927

Alternate names for this biomarker include:

C-X-C motif chemokine 1, Angie, B cell-attracting chemokine 1, BCA-1, CXC chemokine BLC, Small-inducible cytokine B13

Simoa™ Services
Biomarker LLOQ*
(Serum and Plasma)
(Undiluted Samples)
Volume Required
Serum or plasma Other fluids**
B Lymphocyte Chemoattractant (BLC, CXCL13) 0.64 pg/mL 0.064 pg/mL 50 µL 150 µL

* Lower limit of quantitation (LLOQ) represents the lowest amount of an analyte that can be quantitatively determined with acceptable precision. LLOQ is determined by performing 2-fold serial dilutions of Standard to be tested in triplicate over three runs. The percent coefficient of variation (CV) is calculated for each of the dilution replicates, and the LLOQ is determined as the concentration at which the CV is 30%.

** Cerebrospinal fluid, urine, tissue culture supernatants,  bronchoalveolar lavage, synovial fluid, tissue extracts, tears, skin washings, etc.

All assay services are performed in our CLIA-certified laboratory.
Intended for Research Use Only.