CD19 Protein, Human (HEK293, mFc)

The CD19 Protein serves as a coreceptor for the B-cell antigen receptor complex (BCR) on B-lymphocytes, playing a pivotal role in decreasing the threshold for activation of downstream signaling pathways and facilitating B-cell responses to antigens. It activates signaling pathways leading to the activation of phosphatidylinositol 3-kinase and the mobilization of intracellular Ca(2+) stores. Although not required for early steps during B cell differentiation in the blood marrow, CD19 is essential for the normal differentiation of B-1 cells. Moreover, it is crucial for normal B cell differentiation and proliferation in response to antigen challenges, influencing serum immunoglobulin levels and the production of high-affinity antibodies in response to antigen challenge. CD19 forms complexes with CR2/CD21, CD81, and IFITM1/CD225 in the membrane of mature B-cells. It interacts directly with CD81, a crucial interaction for trafficking and compartmentalization of the CD19 receptor on the cell surface of activated B cells. Additionally, CD19 interacts with VAV, GRB2, SOS, PLCG2, LYN, and the regulatory p85 subunit of phosphatidylinositol 3-kinase when phosphorylated on specific tyrosine residues.