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A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. [1] Lymphocytes include T cells (for cell-mediated and cytotoxic adaptive immunity), B cells (for humoral, antibody-driven adaptive immunity), [2] [3] and innate lymphoid cells (ILCs; "innate T cell-like" cells involved in mucosal immunity and homeostasis), of which natural killer cells are an ...
The T cell-dependent processes are subdivided into primary and secondary responses: a primary response (meaning that the T cell is present at the time of initial contact by the B cell with the antigen) produces short-lived cells that remain in the extramedullary regions of lymph nodes; a secondary response produces longer-lived cells that ...
Of the three B cell subsets, FO B cells preferentially undergo T cell-dependent activation while MZ B cells and B1 B cells preferentially undergo T cell-independent activation. [ 16 ] B cell activation is enhanced through the activity of CD21 , a surface receptor in complex with surface proteins CD19 and CD81 (all three are collectively known ...
They present the antigen to T cells and, if there is a T cell with the appropriate T cell receptor, it will be activated. [25] B cells acquire antigen directly from the afferent lymph. If a B cell binds its cognate antigen it will be activated. Some B cells will immediately develop into antibody secreting plasma cells, and secrete IgM.
Additionally, the T cells are able to help the B cells by the interaction of the T cell CD40 ligand with the B cell CD40 molecule, which causes a signaling cascade that is beneficial for the survival and proliferation of B cells. B cell receptor activation results in the activation of the NF-kB signaling pathway, which is essential for the ...
T cells are grouped into a series of subsets based on their function. CD4 and CD8 T cells are selected in the thymus, but undergo further differentiation in the periphery to specialized cells which have different functions. T cell subsets were initially defined by function, but also have associated gene or protein expression patterns.
In immunohistochemistry and flow cytometry, antibodies to TdT can be used to demonstrate the presence of immature T and B cells and pluripotent hematopoietic stem cells, which possess the antigen, while mature lymphoid cells are always TdT-negative. While TdT-positive cells are found in small numbers in healthy lymph nodes and tonsils, the ...
When the first immortalized T cell lines began to emerge, it became possible to observe which T cells had specific effects on B cells. Various T cell types secreted factors that induced Ig production, in some cases only of specific kinds or only in the presence of antigen. Some IgG classes secreted by B cells are exclusively T cell dependent. [7]