Expressed on follicular dendritic cells and B cells.

A B cell specific transmembrane glycoloproteins expressed on the cell surface from late pro B to early pre-B cell stages, with increasing expression as B cells mature.

CD19 is a transmembrane glycoprotein that is a member of the immunoglobulin super family and an important regulator of  B cell signaling and B cell activation.

Its expression at all stages of B-cell differentiation except for hematopoetic stem cells it is considered a reliable B-cell bio marker.

CD19 is expressed more broadly than CD 20 particularly on plasmablasts and the majority of plasma cells.

CD19 is a protein is expressed on the surface of B cells from early stages of development and is expressed on most B-cell malignancies.

On B cells from earliest recognizable B-lineage cells during development to B-cell blasts but is lost on maturation to plasma cells.

As a central signaling component of cell surface complexes that can include CD 21, CD 81, and CD 225, CD 19 links the innate and adaptive arms of the immune system.

It is broadly and homogeneously expressed across B cell malignancies and is able to enhance B cell antigen receptor signaling, representing an important signaling component for the survival and proliferation of malignant B cells.

CD19 expression on B-cell surface continues from the lineage commitment during the stem cell differentiation until it is down regulated during terminal differentiation into plasma cells.

The antigen CD19 has wide expression across a wide range of B-cell cancers and has restricted expression in healthy tissues.

CD 19 expression maintained in B-lineage that undergo neoplastic transformation have a high density of expression.

It primarily acts as a B cell co-receptor in conjunction with CD21 and CD81.

Upon activation, the cytoplasmic tail of CD19 becomes phosphorylated which leads to binding by Src-family kinases and recruitment of PI-3 kinase.

Targeting CD19 can lead to B-cell aplasia and hypogammaglobulinemia.
B- cell-recovery has been observed two years after receiving anti-CD CAR T-cell therapy.
Targeting CD19 with CAR T Cells has an associated response rate of 70-90% even in patients who have failed with autologous transplant for DLBCL.
Using CAR T CD 19 Cells, may be efficacious in the treatment of auto immune diseases, affecting plasmablasts and plasma cells which have been identified as critical for autoimmunity.

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