1. Definition
B lymphocytes, also known as B cells, are a type of white blood (leukocytes) cell that play a crucial role in the adaptive immune system, primarily responsible for the humoral immune response by producing antibodies.
2. Physiological Count
The normal physiological count of B lymphocytes in peripheral blood ranges from 100 to 600 cells/µL in healthy individuals. This number can vary slightly based on factors such as age, gender, and overall health.
3. Pathological Count
- Low B Cell Count
- High B Cell Count
4. Classification
B cells can be classified into several subsets based on their function and maturation stage:
- Naïve B Cells: These cells have not yet encountered an antigen and circulate through lymphoid organs
- Memory B Cells: These long-lived cells have encountered their specific antigen and are capable of mounting a faster and stronger response upon re-exposure
- Plasma Cells: Differentiated B cells that produce large amounts of antibodies during an immune response
5. Origin
- Source: Hematopoietic stem cells in the bone marrow
- Developmental Stages:
- Pro-B cell
- Pre-B cell
- Immature B cell
- Mature naïve B cell
- Maturation: Occurs entirely in the bone marrow, where B cells develop functional B cell receptors (BCRs)
- Antigen Exposure: Naïve B cells migrate to peripheral lymphoid organs (e.g., spleen, lymph nodes) to encounter antigens
6. Function
- Antibody Production: Synthesize and secrete antibodies in response to specific antigens
- Humoral Immunity: Participate in the humoral immune response by producing antibodies that neutralize pathogens
- Antigen Presentation: Present processed antigens to T cells via MHC class II molecules
- Cytokine Secretion: Produce cytokines that influence other immune cells and modulate immune responses
- Immunological Memory: Form memory B cells after initial exposure to an antigen, providing long-lasting immunity