How B cells are activated?
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How B cells are activated?
B cells are activated when their B cell receptor (BCR) binds to either soluble or membrane bound antigen. In their inactivated state B cells express IgM/IgD but once activated they may express IgA, IgE, IgG or retain IgM expression. They do this by excision of the unwanted isotypes (Figure 1).
How are the B cells activated to respond to a pathogen?
During immune responses, B cells are directly activated by invading microorganisms, either by detecting a specific antigen through their BCR or by detecting pathogen-associated molecular patterns (PAMPs) through general pattern recognition receptors (PRRs)4,5,6 (Fig. 1).
How do B cells respond to the initial exposure to an antigen?
Each B cell has a specific antibody as a cell surface receptor. Following initial exposure to antigen, the plasma cells stop producing antibody and die. Memory cells remain in greater numbers than the initial B cells, allowing the body to quickly respond to a second exposure of that antigen.
What antigens can stimulate B cells to become activated?
T-independent antigens can stimulate B cells to become activated and secrete antibodies without assistance from helper T cells. These antigens possess repetitive antigenic epitopes that cross-link BCRs.
How do you activate naive B cells?
Naive B cells activated after primary antigen encounter initially produce antigen-specific immunoglobulin (Ig) M, and later IgG, followed by GC formation. The response reaches its maximum at approximately 2 weeks after stimulation, accompanied by increased antibody affinity as mutations accumulate in the IgV regions.
How do viruses activate B cells?
Induction of virus-induced B cell responses requires B cell activation through binding of cognate antigens to the BCR. In the spleen and LN, B cells are confined predominantly to the follicles. Mutiple well-regulated mechanisms ensure effective exposure of naive B cells to viral antigens.
How do B lymphocytes become activated and respond to viral infection?
B cells might also directly capture and/or express viral antigens in the lymph nodes or at site of infection for transport to the lymph nodes (80). Following their antigen-induced activation, B cells are responding with the induction of either extrafollicular responses or germinal centers (Fig. 2).
How does an antigen stimulate an immune response?
Specific immune responses are triggered by antigens. Antigens are usually found on the surface of pathogens and are unique to that particular pathogen. The immune system responds to antigens by producing cells that directly attack the pathogen, or by producing special proteins called antibodies.
How B cells become stimulated and activated?
Activation of B cells
- A B cell becomes activated when its receptor recognizes an antigen and binds to it.
- Most antigens are T-dependent.
- Interaction with antigens causes B cells to multiply into clones of immunoglobulin-secreting cells.
- The process just described takes place among the circulating B lymphocytes.
Can antigens stimulate B cells directly?
Some microbial antigens can activate B cells directly in the absence of T-cell help. The ability of B cells to respond directly to these antigens provides a rapid response to many important bacterial pathogens.