CD19: A coreceptor modulating B-cell receptor signaling and activation

• Gene Information: Located on chromosome 16p11, the CD19 gene encodes a highly conserved 95 kDa type I transmembrane glycoprotein belonging to the immunoglobulin superfamily. 
• Protein Expression: CD19 expression is strictly restricted to the B-cell lineage, appearing from the early pre-B cell stage and maintaining throughout differentiation until it is lost during plasma cell maturation.
• Signaling Pathway: Upon recruitment, CD19 forms a complex with CD21 and CD81 to amplify B-cell receptor signaling, recruiting PI3K and activating the downstream AKT pathway to drive cellular proliferation.
• Therapeutic Inhibition: CD19 is a premier target for immunotherapy; monoclonal antibodies, bispecific T-cell engagers like blinatumomab, and CD19-directed CAR-T cell therapies are widely used to eradicate malignant B cells.

Strain specific CD19 expression analysis in wild-type C57BL/6JNifdc mice and homozygous humanized B-hCD19 mice ad by flow cytometry.
Splenocytes were collected from wild-type C57BL/6JNifdc mice and homozygous B-hCD19 mice ad. Protein expression was analyzed with anti-mouse CD19 antibody (Biolegend, clone 6D5, 115507) and anti-human CD19 antibody (Biolegend, clone 4G7, 392503) by flow cytometry.

Strain specific CD19 expression analysis in wild-type C57BL/6JNifdc mice and homozygous humanized B-hCD19 mice ad by flow cytometry.
Lymph nodes were collected from wild-type C57BL/6JNifdc mice and homozygous B-hCD19 mice ad. Protein expression was analyzed with anti-mouse CD19 antibody (Biolegend, clone 6D5, 115507) and anti-human CD19 antibody (Biolegend, clone 4G7, 392503) by flow cytometry.

Strain specific CD19 expression analysis in wild-type C57BL/6JNifdc mice and homozygous humanized B-hCD19 mice ad by flow cytometry.
Blood cells were collected from wild-type C57BL/6JNifdc mice and homozygous B-hCD19 mice ad. Protein expression was analyzed with anti-mouse CD19 antibody (Biolegend, clone 6D5, 115507) and anti-human CD19 antibody (Biolegend, clone 4G7, 392503) by flow cytometry.

Strain specific CD19 expression analysis in wild-type C57BL/6JNifdc mice and homozygous humanized B-hCD19 mice ad by flow cytometry.
Bone marrow was collected from wild-type C57BL/6JNifdc mice and homozygous B-hCD19 mice ad. Protein expression was analyzed with anti-mouse CD19 antibody (Biolegend, clone 6D5, 115507) and anti-human CD19 antibody (Biolegend, clone 4G7, 392503) by flow cytometry.

Analysis of T-cell subpopulations by flow cytometry in spleen.
Splenocytes were isolated from C57BL/6JNifdc mice and homozygous B-hCD19 mice (female, 8-week-old, n = 3). Single live cells were analyzed by flow cytometry as indicated. Values are expressed as mean ± SEM.

Analysis of T-cell subpopulations by flow cytometry in lymph nodes.
Lymph nodes were isolated from C57BL/6JNifdc mice and homozygous B-hCD19 mice (female, 8-week-old, n = 3). Single live cells were analyzed by flow cytometry as indicated. Values are expressed as mean ± SEM.

Analysis of T-cell subpopulations by flow cytometry in blood.
Peripheral blood cells were isolated from C57BL/6JNifdc mice and homozygous B-hCD19 mice (female, 8-week-old, n = 3). Single live cells were analyzed by flow cytometry as indicated. Values are expressed as mean ± SEM.

Analysis of T-cell subpopulations by flow cytometry in bone marrow .
Bone marrow was isolated from C57BL/6JNifdc mice and homozygous B-hCD19 mice (female, 8-week-old, n = 3). Single live cells were analyzed by flow cytometry as indicated. Values are expressed as mean ± SEM.