If a viral antigen were to bind to the receptors on the surface of a B lymphocyte, which of the following immune responses would NOT occur?

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Quizplus · Accepted Answer

11ecba2d_1022_9864_a3bf_373b98be9cf7_MD0008_00 The immune response is divided into innate and adaptive immunity. The innate immune system comprises the skin and mucous membranes, as well as specialized proteins and cells that rapidly and nonspecifically recognize and destroy antigens. In contrast, the adaptive immune system comprises cells that mount specialized immune responses based on the learned recognition of specific antigens. The adaptive immune response is further subdivided into cell-mediated immunity and humoral immunity. Humoral immunity, specifically, is driven by B lymphocytes that secrete antibodies, specialized proteins that recognize specific foreign antigens (ie, molecules targeted by the immune system). These antibodies circulate throughout the blood and lymph, binding foreign antigens and marking them for destruction by other immune cells. A mature B lymphocyte is inactive until its receptors bind a specific foreign antigen. On activation by antigen binding, the B lymphocyte endocytoses (engulfs) the antigen, breaking it down into smaller fragments. Within the B lymphocyte, specialized antigen-binding molecules called major histocompatibility class II (MHC II) proteins bind the antigen fragments. MHC-antigen complexes are transported to the surface of the B lymphocyte and integrate into the cell membrane, allowing antigen fragments to be displayed outside the cell and presented to other immune cells known as helper T cells. On binding antigens presented by B lymphocytes, helper T cells release cytokines (signaling molecules) that stimulate B-lymphocyte proliferation (Choice B). This produces many identical B lymphocytes that may differentiate into either of the following cell types: Short-lived plasma cells secrete antibodies during the immediate immune response (Choice A). Long-lived memory cells remain in lymphoid tissues for a long time and can recognize the antigen more rapidly in the event of a future infection (Choice D). (Choice C) Natural killer and cytotoxic T cells, not B lymphocytes, respond to antigens by releasing toxins that induce apoptosis (cell death) in nearby infected cells. Educational objective: Humoral immunity is an antibody-mediated immune response. During an infection, B lymphocytes bind foreign antigens and become activated. Activated lymphocytes divide into many identical cells, some of which differentiate into short-lived plasma cells that secrete antibodies during the immediate immune response. The remaining cells differentiate into long-lived memory cells, which can respond more rapidly to future infections.

If a Viral Antigen Were to Bind to the Receptors