B lymphocytes or B cells and T lymphocytes or T cells are the major players in adaptive immune response. T cells mediate cell mediated immunity whereas B cells are behind antibody mediated or humoral immunity. They possess antigen binding cell surface receptors responsible for specificity, diversity memory and self/non-self recognition by the immune system.
See the Difference between B cells and T cells
B cells originate and mature in bone marrow itself. Two major functions of B cells are
  • they differentiate into plasma cells that produce antibodies; and memory B cells that is responsible for immunologic memory
  • B cells acts as antigen presenting cells (APCs)
Difference between B cells and Plasma cells (B cells vs Plasma cells)
B cells
Plasma cells
B Cells possess a surface B Cell receptor (BCR) composed of surface immunoglobulin (Ig) for antigen binding and a transmembrane protein made up of two heterodimer subunits of Ig-α and Ig-β  called as CD79 for signal transduction
Plasma cells lacks surface receptors like BCR
B cells are formed from hoematopoetic stem cells of bone marrow
Plasma cells are formed by the differentiation of B cells upon activation
Naive B cells do not secrete antibodies
High rate of secretion of antibodies by plasma cells
B Cells has MHC class II receptor as it functions as antigen presenting cells (APC)
Mature plasma cells lacks MHC class II receptor
Common mature B cell markers are CD19, CD 20, CD21, CD22
Plasma cells often express Syndecan1 (CD138), CD44 and VLA-4 on their surface (common markers)
B cells in peripheral lymphoid tissue are predominantly long-lived, with a life span of between 4 and 7 weeks
Plasma cells may be short‐lived, surviving only 3–5 days often found in the secondary lymphoid tissue. Generally, these secrete lower affinity antibody. Alternatively, plasma cells may be long‐lived, surviving decades or the lifetime of an animal, secreting high‐affinity antibody majority of which found in the bone marrow
*Antibody class switching and somatic hypermutation occurs in mature B cells in response to antigen stimulation and costimulatory signals.
No such mechanisms reported so far in plasma cells
 *Immunoglobulin class switching, also known as isotype switching, isotypic commutation or class-switch recombination (CSR), is a biological mechanism that changes a B cell's production of immunoglobulin (antibodies) from one type to another, such as from the isotype IgM to the isotype IgG.
Wang, K., Wei, G., & Liu, D. (2012). CD19: a biomarker for B cell development, lymphoma diagnosis and therapy. Experimental hematology & oncology, 1(1), 36.

Anaya, J. M., Shoenfeld, Y., Rojas-Villarraga, A., Levy, R. A., & Cervera, R. (2013). Autoimmunity: From Bench to Bedside. El Rosario University Press.Fulcher, D. A., & Basten, A. (1997). B cell life span: a review. Immunology and cell biology75(5), 446-455.Stavnezer, J., Guikema, J. E., & Schrader, C. E. (2008). Mechanism and regulation of class switch recombination. Annual review of immunology, 26, 261-92.

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