What is the difference between Ti 1 and Ti-2 antigens?
There are 2 distinct subgroups of TI antigens, different in mechanism of activating B lymphocytes. TI-1 antigen, which has an activity that can directly activate B cells and TI-2 antigen, which has highly repetitive structure and causes simultaneous cross-linking of specific B cell receptors (BCR) on B lymphocyte.
What is a Ti-2 antigen?
TI-2 antigens include polysaccharides, glycolipids, and nucleic acids. When T cells and macrophages are depleted, no antibody response develops against them. A comparison of thymus-dependent and thymus-independent antigens is shown in Table 2.4.
What are TI and TD antigens?
The B-cell response to thymus-dependent (TD) antigens requires direct contact with TH cells, not simply exposure to TH-derived cytokines. Antigens that can activate B cells in the absence of this kind of direct participation by TH cells are known as thymus-independent (TI) antigens.
What does TI antigen mean?
TI stands for Thymus Independent, and it means that the B cell can make antibodies without T cells.
What are antigen presenting cells?
Definition. Antigen-presenting cells (APCs) are a heterogeneous group of immune cells that mediate the cellular immune response by processing and presenting antigens for recognition by certain lymphocytes such as T cells. Classical APCs include dendritic cells, macrophages, Langerhans cells and B cells.
What do Superantigens do?
Superantigens (SAgs) are a class of antigens that result in excessive activation of the immune system. Specifically it causes non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release.
What is the meaning of thymus independent B cell activation Mcq?
Explanation: In thymus independent B-cell pathway, antigen activates B-cell without the participation of TH cell. Response generated by thymus independent antigens only generate IgM and do not give rise to memory.
Where do B cells go after maturation?
B cell activation occurs in the secondary lymphoid organs (SLOs), such as the spleen and lymph nodes. After B cells mature in the bone marrow, they migrate through the blood to SLOs, which receive a constant supply of antigen through circulating lymph.
Can you produce T cells without a thymus?
After puberty the thymus shrinks and T cell production declines; in adult humans, removal of the thymus does not compromise T cell function. Children born without a thymus because of an inability to form a proper third pharyngeal pouch during embryogenesis (DiGeorge Syndrome) were found to be deficient in T cells.
What is the difference between Ti1 and Ti2 antigens?
Unlike TI-1 antigens, TI-2 antigens do not act as polyclonal activators, activate only mature B cells, and may require cytokines derived from TH cells. Antigens that stimulate B-cells directly, without co-stimulation by helper T-cells
How do TI-1 antigens activate B cells?
Most TI-1 antigens are polyclonal B-cell activators (mitogens); i.e. they are able to activate B cells regardless of their antigenic specificity.
What is titi-1 antigen?
TI-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. TI-1 antigens activate B-cells via Toll like receptors, which are, in human, expressed on the surface…
What are Ti independent antigens?
T Independent (TI) Antigen A typical large polysaccharide is made up of repeating sequences of few simple sugars so it has multiple copies of identical antigenic determinants. When specific naïve B cells come in contact with such antigens, these antigenic determinants bind the surface IgM and IgD receptors.