CD19+ B cells, or B lymphocytes, are a type of immune cell derived from the common lymphoid progenitor in the bone marrow. B lymphocytes play a significant role in humoral immunity by producing antibodies which neutralize microorganisms and initiating signaling pathways for other immune cells.
B cells develop in the primary lymphoid tissues, which includes fetal liver and bone marrow. Following initial development, B cells migrate to the lymph nodes and spleen for functional maturation.
In addition to producing antibodies to fight disease, CD19+ B cells directly and indirectly initiate other effector mechanisms of the immune system. These mechanisms include phagocytosis, obstructing secreted virulence components, activating the complement cascade, and inducing antibody-mediated cellular cytotoxicity.
B cells also function as antigen-presenting cells, which activate T cells to fight an infection.
B cells become activated when a B cell receptor (BCR) binds to the epitopes of an antigen. This antigen and B lymphocyte immune reaction is called clonal selection.
Upon activation, B cell undergoes a process of clonal expansion in which B cell (parent cell) divides to form two daughter cells. This results in multiple copies of B cells that possess specificity and binding affinity for the same antigen.
The daughter cells later differentiate into both short- and long-lived B cells. The former is the plasmablasts that provide immediate protection, whereas the latter are plasma and memory B cells that give long-lasting immune protection from harmful entities.
The figure below describes the B cell activation process and response to a viral infection:
B Cell Activation Process
CD19+ is the most crucial stimulatory co-receptor of B lymphocytes. It plays a substantial part in controlling the activation of B cells and their role in autoimmunity.
The CD19+ molecule is also involved in the B cell subsets development and mature B cell response to T cell-dependent and independent antigens.
The CD19+ receptor expresses on pro-B cells during their early developmental stages. It continues to express during the differentiation process of B cells into the plasmablast stage.
How Are CD19+ B Cells Used in Research?
CD19+ B cells have many potential uses in advanced research activities:
Studying Immune Responses
B cells are commonly used to study vaccine candidates that elicit protective antibodies and antibody-mediated autoimmune diseases, such as rheumatoid arthritis and lupus.
In addition, there’s been a significant increase in research published over the past five years related to antigen-specific B cells. Scientists continue to develop technologies that take advantage of the specificity of BCR-associated and secreted antibodies to study the immune response to disease.
The CD19 receptor is expressed mainly on all B-cell malignancies. Thus, critically contribute to the development of B cell tumors.
Moreover, it is also involved in upregulating the cellular expression of proto-oncogenes, i.e., C-Myc, mutated in most cancers. Thereby, targeting CD19 can do wonders in cancer immunotherapy.
Diagnosing B Cell Lymphomas
CD19 receptor is considered an advanced biomarker to diagnose B cell lymphomas and tumors. Additionally, it is a potential target for lymphoma therapies.
Autoantibodies are one of the main culprits of autoimmunity. Therefore, antibody-producing B cells and their molecular signaling can be studied, and are particularly aimed as a possible target for treating autoimmune diseases.
Currently, CD19+ B cells are a research focus as they are mainly expressed in the early stages of B cell development than the other receptors.
Further, monoclonal antibodies that target CD19+ B cells as therapeutic agents i.e., Inebilizumab, Blinatumomab, and Rituximab can be researched.
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