B Cells
The principal function of B cells is to make antibodies against soluble antigens. B cell recognition of antigen is not the only element necessary for B cell activation (a combination of clonal proliferation and terminal differentiation into plasma cells).
Naïve B cells can be activated in a T-cell dependent or independent manner, but two signals are always required to initiate activation.
B cell activation depends on one of three mechanisms: Type 1 T cell-independent (polyclonal) activation, Type 2 T cell-independent activation (in which macrophages present several of the same antigen in a way that causes cross-linking of antibodies on the surface of B cells), and T cell-dependent activation. During T cell-dependent activation, an antigen presenting cell (APC) presents a processed antigen to a helper T (Th) cell, priming it. When a B cell processes and presents the same antigen to the primed Th cell, the T cell releases cytokines that activate the B cell.
Read more about this topic: Humoral Immunity
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