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Acquired immunity depends upon the interaction between antigens and a group of proteins called antibodies produced by B cells of the blood. There are many antibodies and each is specific for a particular type of antigen. Thus immune response in acquired immunity is due to the precise binding of antigens to antibody.
B cells produce antibody molecules which may be either secreted or inserted into the plasma membrane where they serve as a part of B-cell receptors. [2] When a naïve or memory B cell is activated by an antigen, it proliferates and differentiates into an antibody-secreting effector cell, known as a plasmablast or plasma cell. [2]
Memory B cells circulate in the blood stream in a quiescent state, sometimes for decades. [1] Their function is to memorize the characteristics of the antigen that activated their parent B cell during initial infection such that if the memory B cell later encounters the same antigen, it triggers an accelerated and robust secondary immune response.
The immune system may respond in multiple ways to an antigen; a key feature of this response is the production of antibodies by B cells (or B lymphocytes) involving an arm of the immune system known as humoral immunity. The antibodies are soluble and do not require direct cell-to-cell contact between the pathogen and the B-cell to function.
After the inflammatory immune response to danger-associated antigen, some of the antigen-specific T cells and B cells persist in the body and become long-living memory T and B cells. After the second encounter with the same antigen, they recognize the antigen and mount a faster and more robust response.
The cells that carry out the adaptive immune response are white blood cells known as lymphocytes. B cells and T cells, two different types of lymphocytes, carry out the main activities: antibody responses, and cell-mediated immune response. In antibody responses, B cells are activated to secrete antibodies, which are proteins also known as ...
The naive B lymphocyte expresses both surface IgM and IgD. The co-expression of both of these immunoglobulin isotypes renders the B cell ready to respond to antigen. [49] B cell activation follows engagement of the cell-bound antibody molecule with an antigen, causing the cell to divide and differentiate into an antibody-producing cell called a ...
B cells are involved in the humoral immune response, whereas T cells are involved in cell-mediated immune response. Killer T cells only recognize antigens coupled to Class I MHC molecules, while helper T cells and regulatory T cells only recognize antigens coupled to Class II MHC molecules. These two mechanisms of antigen presentation reflect ...