24. Is there memory in a thymus-independent antibody response? What molecule stimulates the T-Independent response
24 A.Yes, in some cases there will be memory in thymus independent antibody response but in general cases no memory is generated in thymus independent antibody response.
B.Molecules like bacterial lipopolysaccharides , bacteria DNA, cytokinesis like interlukins and interferons stimulate T-independent response
Explanation :- There are two type of immune response- T-dependent and t-independent. The B-cell response to thymus-dependent (TD) antigens requires direct contact with TH cells and 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. TI antigens are divided into types 1 and 2, and they activate B cells by different mechanisms.
TI-1 antigens activate B-cells via Toll like receptors, which are, in human, expressed on the surface of B lymphocytes after BCR stimulation.In higher concentrations, TI-1 antigens bind to BCR and TLR of various clones of B lymphocytes, which leads to production of multiclonal antibodies. But when the concentration of TI-1 is lower, it can activate only B lymphocytes with specific binding of TI-1 on their BCR, and leads to production of monoclonal antibodies.An example of TI-1 antigen is lipopolysaccharide (LPS) or bacterial DNA. When a specific naïve B cells come in contact with such antigens, these antigenic determinants bind the surface IgM and IgD receptors. This binding leads to clustering of surface immunoglobulins which generates a signal, strong enough to activate the naïve B cells. This activated B cells produces and releases first immunoglobulin i.e. IgM. Most TI-1 antigens are polyclonal B-cell activators (mitogens); i.e. they are able to activate B cells regardless of their antigenic specificity. At higher concentrations, some TI-1 antigens will stimulate proliferation and antibody secretion by as many as one third of all B cells but in lower concentrations of TI-1 antigens, only those B cells specific for epitopes of the antigen will be activated.
2.TI type 2 activate immune response by cytokins like interleukin and interferon. It consists mainly of highly repetitive surface structures (epitopes) of encapsulated bacteria. The activation of B lymphocytes is caused by cross-linking of a critical number of B cell receptors, which leads to accumulation of BCRs and cross activation of these receptors. It results in proliferation and differentiation of B lymphocytes and production of antibodies. TI-2 antigens can activate only mature B lymphocytes. Hence no memory.
But in some cases where type 2 antigen epitopes cross linked with multiple BCRs for long durations like in conjugate vaccines then B cell activation takes place and switching of BCRs i.e Ig takes places which produces memory.
InEven though the response on TI antigens is not dependent on T lymphocytes, there are some cytokines, produced mainly by T lymphocytes and natural killer (NK) cells, necessary for eliciting reaction against these antigens. The most necessary are interleukin 2 (IL-2), interleukin 3 (IL-3) and interferon γ(IFN-γ). Moreover, additional stimulation by dendritic cells (DC) and macrophages is required.
24. Is there memory in a thymus-independent antibody response? What molecule stimulates the T-Independent response
Memory B cells make a significant contribution O primary antibody response nonspecific host resistance cell-mediated immunity secondary antibody response Question 36 (1 point) Phagocytosis and inflammation are O secondary antibody response Ocell-mediated immunity nonspecific host resistance primary antibody response
24) The aspect of the immune response that vaccines are based on is A) stimulation of phagocytosis. B) protection of the normal microbiota. C) inflammation and fever. D) stimulation of cellular, as opposed to humoral, immunity. E) production of memory cells and high antibody titers from pathogen exposure
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