B Cells, Memory B Cells and Plasma Cells: B Cell Activation, Development and the B Cell Receptor.
Автор: Vision BioLearning
Загружено: 2024-04-30
Просмотров: 455
Introduction: B cells, also known as B lymphocytes, are a crucial component of the adaptive immune system. They are responsible for producing antibodies and driving the humoral immune response against pathogens and foreign substances.
B Cell Development and Activation: B cells develop from hematopoietic stem cells in the bone marrow, undergoing a process called V(D)J recombination to generate a diverse repertoire of B cell receptors (BCRs). Immature B cells are selected to eliminate self-reactive cells, and mature B cells migrate to peripheral lymphoid organs.
Upon encountering a specific antigen, B cells become activated through BCR signaling and co-stimulation from helper T cells (T cell-dependent activation) or directly by repetitive antigens (T cell-independent activation). Activated B cells proliferate and differentiate into antibody-secreting plasma cells or long-lived memory B cells.
Plasma Cells and Memory B Cells: Plasma cells are terminally differentiated B cells that secrete large quantities of antibodies. Short-lived plasma cells produce IgM, while long-lived plasma cells undergo affinity maturation and class switching to produce higher-affinity antibodies of different classes (IgG, IgA, IgE).
Memory B cells are long-lived cells that rapidly respond to subsequent encounters with the same antigen, providing a robust and rapid antibody response. They express class-switched surface immunoglobulins and are poised to differentiate into plasma cells upon re-exposure.
B Cell Disorders: Dysfunctions in B cells can lead to various disorders, including:
1. Autoimmune diseases (e.g., systemic lupus erythematosus), where self-reactive B cells produce autoantibodies against the body's own tissues.
2. Hypersensitivities (e.g., allergies), involving excessive or inappropriate antibody production against harmless antigens.
3. Immunodeficiencies (e.g., X-linked agammaglobulinemia), characterized by impaired B cell development or function, leading to increased susceptibility to infections.
4. B cell malignancies (e.g., lymphomas, leukemias), resulting from uncontrolled proliferation of abnormal B cells.
Conclusion: B cells play a pivotal role in the adaptive immune response by producing antibodies and generating immunological memory. Understanding their development, function, and associated disorders is crucial for developing effective therapies and advancing our knowledge of the immune system.
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