A Review of Classic Physiological Systems
Len Wisneski in The Scientific Basis of Integrative Health, 2017
When a B cell encounters an offending antigen, it transforms into a plasma cell, which secretes substances called immunoglobulins (IgG, IgA, IgM, IgD, and IgE). These are antibodies. They bind to the pathogen and, along with other immune system components, inactivate it. IgG is the most common, comprising 75%–85% of the total serum immunoglobulin. Typically, a blood test is used to measure these antibodies, but IgA, for example, is produced in and can be measured from saliva. Memory B cells are a type of memory cell with the capacity to remember previous exposure to an antigen and, thus, to hasten the immune response upon a subsequent encounter. Both memory B cells and memory T cells are efficient immune response cells. The cells are stored in the lymphatic tissue, waiting for a returning invader. Vaccines permit an initial, relatively mild exposure to an antigen, but they result in storage of the memory cells that can later prevent the illness.
Structure and function of skin
Roger L. McMullen in Antioxidants and the Skin, 2018
The adaptive immune system is typically classified into two types of immune response depending on the nature of its course. The humoral immune response occurs when free antigen activates B cells resulting in the manufacture of antibodies, which are then able to circulate in the blood. In contrast, the cell-mediated immune response does not involve the expression of antibodies but does depend on the action of helper T cells. Figure 1.16 provides a diagrammatic overview of both immune responses as well as the communication between the two routes via cellular signaling. As seen in the figure, the primary feature of the humoral response is the direct interaction of a free antigen with a B cell, which contains a surface receptor capable of binding the antigen. In fact, the surface receptor of the B cell is an antigen receptor (immunoglobulin). Once antigen binding has taken place, the B cell expresses the appropriate antibody. It is important to bear in mind that only B cells are capable of expressing antibodies. This gives rise to the proliferation of memory B cells as well as plasma cells. The memory B cells can be utilized for future encounters with the same antigen. The plasma cells, on the other hand, circulate through the blood and secrete antibodies to fight off antigens in the system.
Monocyte and lymphocyte membrane markers: Ontogeny and clinical significance
Gabriel Virella in Medical Immunology, 2019
Some studies have shown that antigen-specific memory B cells can persist for decades without the presence of cognate antigen. Human memory B cells are characterized by CD27 expression and typically display a phenotype of CD20+, CD38−, CD27+, CD80+, CD84+, and CD86+. Since these cells have high affinity for antigen and elevated expression of co-stimulatory molecules, once reactivated by antigen encounter and T cell help, they exhibit a greater capacity to rapidly proliferate and differentiate into antibody-secreting cells compared to naïve B cells. The hyper-response of memory B cells following reexposure to antigen results in the generation of high titers of high-affinity antibodies and promotes clearance of the antigen.
Increased Non-switched Memory B Cells are Associated with Plasmablasts, Serum IL-6 Levels and Renal Functional Impairments in IgAN Patients
Published in Immunological Investigations, 2020
Rui Si, Pingwei Zhao, Zhenxiang Yu, Zhihui Qu, Weixia Sun, Tao Li, Yanfang Jiang
B cells are important for humoral responses and can present antigen. Previous studies have shown that B cells are crucial for the pathogenesis of several autoimmune diseases (Gang et al. 2011; Wu et al. 2013). Following exposure to antigen, B cells can activate and differentiate into memory B cells, plasmablasts and plasma cells. Memory B cells respond to further antigen challenge by rapid and stronger humoral responses due to their proliferation and becoming antibody-secreting plasmablasts (Oleinika et al. 2019). Human memory B cells can be generated at different stages of differentiated B cells and classified into CD3-CD19+CD27+IgD+IgM+ non-switched memory B cells, CD3-CD19+CD27+IgD-IgM+ IgM-only memory B cells, CD3-CD19+CD27+IgD-IgM- switched memory B cells, CD3-CD19+CD27-IgM-IgD- double negative (DN) memory B cells (Agematsu et al. 2000; Klein et al. 1998). A previous study has indicated that the frequency of circulating CD19+CD27+ memory B cells increases in IgAN patients (Wang et al. 2014). However, the function of different subsets of memory B cells in the development of IgAN has not been clarified.
Current strategies for detecting functional convergence across B-cell receptor repertoires
Published in mAbs, 2021
Matthew I. J. Raybould, Anthony R. Rees, Charlotte M. Deane
The naïve component of the immune response should be strongest in the first week(s) following exposure, overtaken thereafter by class-switched plasma cells that over time benefit from increased levels of affinity maturation.58 Antigen-complementary memory B-cells can either be detected in high concentration soon after exposure, or can develop only after antigen-encounter if the subject was originally immunologically-naïve to the pathogen.59 Early differentiated memory cells (IgM+) are typically of moderate affinity but high promiscuity, able to respond to a range of homologous antigens (e.g. viral variants), while later-differentiated class-switched (IgM− and IgG+/IgA+) memory B-cells are likely to have higher affinity to the initial immunogen but may exhibit a narrower functional profile.60
B cells and upper airway disease: allergic rhinitis and chronic rhinosinusitis with nasal polyps evaluated
Published in Expert Review of Clinical Immunology, 2021
Harsha H Kariyawasam, Louisa K James
B-cell memory is provided by both memory B (CD19+) cells and long-lived plasma cells (CD138+). Plasma cells are terminally differentiated and function solely to secrete very high quantities of antibody. Whereas plasma cells that originate early on in the B-cell response, prior to germinal center formation, are relatively short-lived (3–5 days), plasma cells that emerge following the germinal center response are remarkably long-lived. These long-lived plasma cells reside in specialized niches such as the bone marrow, spleen and gut, supported by cytokines including IL-6 and APRIL produced by stromal cells [45], where they may survive for up to the lifetime of the host and continually secrete antibody at a rate of over 108 antibody molecules per hour [49]. Memory B cells represent a heterogeneous subset of B cells but are essentially characterized as long-lived quiescent B cells capable of being reactivated by secondary antigen exposure. When exposed to antigen, memory B cells can either form new germinal center responses or can rapidly differentiate to plasma cells to produce affinity-matured antibody. These fate choices are determined in part by whether the memory B cell had undergone antibody class switching with unswitched memory B cells more likely to form new germinal center responses whereas switched memory B cells are more likely to differentiate into plasma cells [50]. Memory B cells can recirculate through SLOs but can also reside within tissues, such as the airway where they play an important role in barrier surveillance [51].
Related Knowledge Centers
- Adaptive Immune System
- B Cell
- Germinal Center
- Immunology
- Lymphatic System
- T Cell
- Antigen
- Immune Response
- B-Cell Receptor
- Follicular B Cell