What is antigen independent phase of B cell development?
B cell development and differentiation occurs in multiple phases. The initial, antigen-independent phase generates mature, immunocompetent B cells that can bind to a unique antigen.
What are antigens and T dependent and T independent antigens?
Antigens that require the help of T cells for B cell activation are thymus-dependent (T-dependent) antigens. Antigens that can stimulate B cells without the help of T cells are thymus- independent (T-independent) antigens.
How are B cells activated by antigen?
B cells are activated when their B cell receptor (BCR) binds to either soluble or membrane bound antigen. This activates the BCR to form microclusters and trigger downstream signalling cascades.
What is antigen independent?
Thymus-independent antigen is an immunogen that can stimulate B cells to synthesize antibodies without participation by T cells. These antigens are less complex than are thymus-dependent antigens.
How do B cells develop?
B cells arise from pluripotent stem cells present in the fetal liver and adult bone marrow. The stem cells progressively develop into pro-B cells, pre-B cells, and immature B cells, which are then exported to the periphery as transitional B cells, primarily localizing to the spleen, and undergo further maturation.
What are the two requirements for B cell activation?
B cell activation is dependent on the sequential integration of at least two signals. The first signal is generated by BCR cross-linking with antigen; the second is provided by interaction of B cells with T-helper cells (Parker, 1993).
What is the main distinction between the pro B cell and pre B cell development stages?
Pro-B cells become pre-B cells when they express membrane m chains with surrogate light chains in the pre-B receptor. Surrogate L chains resemble actual L chains but are the same on every pre-B cell.
What is at independent antigen?
T-Independent-1 antigen TI-1 antigens have an intrinsic B cell activating activity, that can directly cause proliferation and differentiation of B lymphocytes without T cell stimulation and independently of their BCR specificity.
What are two types of B cells?
There are four main types of B cells – transitional, naive, plasma, and memory – that all have their own purpose in the maturation process.
Which genes are turned on and off during B cell development?
Genes encoding proteins required for somatic recombination and receptor expression are turned on and off at set times during B cell development. RAG-1, RAG-2, and TdT are expressed only during the times somatic recombination is occurring: early and late pro-B cell and small pre-B cell stages.
What are the different stages of B cell development?
The major developmental stages of the maturation phase include the HSC, the MPP, the CLP, the pro-B cell (progenitor B cell), the pre-B cell (precursor B cell), the immature naïve B cell, the transitional B cell and the mature naïve B cell.