CD19

B-lymphocyte antigen CD19 (CD19), also known as B4, is an IgSF surface glycoprotein of 95 kDa encoded by CD19 gene in humans. It mainly assembles with the antigen receptor of B-lymphocytes in order to decrease the threshold for antigen receptor-dependent stimulation. It is the most common marker of B cell.

The Structure of CD19

CD19 is type I one-pass transmembrane protein, with a single transmembrane domain, a cytoplasmic C-terminus, and extracellular N-terminus. The extracellular domain contains two C2-type Ig-like domains separated by small helical non-Ig domain with possible disulfide links, as well as N-linked carbohydrate addition sites. The highly conserved cytoplasmic domain consists of 242 amino acids with nine tyrosine residues near the C-terminus. No significant homology exists between CD19 and other known proteins.

The Function of CD19

CD19 is critically involved in establishing intrinsic B cell signaling thresholds through modulating both B cell receptor (BCR)-dependent and independent signaling. CD19 is thus critical for the body to mount an optimal immune response. CD19 works in complex with the BCR and other surface molecules to allow both direct and indirect recruitment and binding of various down-stream protein kinases.

Multiple studies have come to suggest that the biologic functions of CD19 are dependent on three cytoplasmic tyrosine residues – Y391, Y482 and Y513. Experiments have shown that substitution of phenylalanine for tyrosine at two of the positions, Y482 and Y513, leads to inhibited phosphorylation of the other seven tyrosines.

The Clinic Significance of CD19

CD19 is one of the important membrane antigens involved in the activation and proliferation of B cells. It is a common surface marker of all B cells. It doesn’t disappear after activation of B cells. In the bulk of the body, the extracellular portion of CD19 binds to other membrane antigens for signal transduction.

CD19-positive cells are elevated in malignant tumors of the B-lymphocyte system, such as CD19 in 95% of acute pre-B lymphocyte leukemia cells and 94% of acute mature B-lymphocytic leukemia cells. Moreover, CD19-positive cells are also found in chronic lymphocytic leukemia and Burkitt lymphoma. CD19-positive cell reduction is seen in humoral immunodeficiency diseases.

Therefore, CD19 detection can make a clear cause diagnosis of the above diseases, and provide a basis for differential diagnosis.

Further Reading: CD19-The Most Popular Target with CAR T-Cell Therapy

CD19 Public Drug Information

1. BLINCYTO TM , also called blinatumomab, is a drug that targets B-lymphocyte antigen CD19. It is developed by Amgen Inc., and the initial approval was in December, 2014. This drug is mainly applied in the treatment of acute lymphoblastic leukaemia (ALL).

2. KYMRIAH, also called tisagenlecleucel, is a drug that targets B-lymphocyte antigen CD19. It is developed by Novartis Pharmaceuticals Corporation., and the initial approval was in August, 2017. This drug is mainly applied in the treatment of acute lymphoblastic leukaemia (ALL).

3. YESCARTA, also called axicabtagene ciloleuce, also is a drug that targets B-lymphocyte antigen CD19. It is developed by Kite Pharma, Incorporated, and the initial approval was in October, 2017. Compared with the two drugs before, this drug is involved in three diseases treatment, including B-cell lymphoma, diffuse large B cell lymphoma and follicular lymphoma.

CD19 Antibodies

CD19 Antibodies for Homo sapiens (Human)

CD19 Proteins

CD19 Proteins for Homo sapiens (Human)

CD19 Proteins for Cavia porcellus (Guinea pig)

CD19 Proteins for Callithrix jacchus (White-tufted-ear marmoset)

CD19 Proteins for Mus musculus (Mouse)

CD19 Proteins for Recombinant Homo sapiens (Human)

CD19 ELISA Kit

CD19 ELISA Kit for Homo sapiens (Human)

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