Question

Given the enormous heterogeneity of antigen receptors expressed on the populations of naive B and T lymphocytes, the adaptive immune response relies on a

process whereby the rare lymphocyte that binds to the antigen is first induced to proliferate, before it can perform its effector function. For B cells, there is a clever mechanism that ensures that the specificity of the antibody secreted by the plasma cell will recognize the same pathogen that initially stimulated the B cell antigen receptor and induced B cell proliferation. This mechanism is:

A. The naive B cell expresses an array of different B-cell antigen receptors, and randomly chooses which specificity of antibody to secrete as a plasma cell.
B. The naive B cell expresses a single specificity of B cell antigen receptor, and then up-regulates the expression of this receptor so it can bind tightly to the pathogen.
C. The plasma cell proliferates after it has finished secreting antibody to generate
more plasma cells with specificity for the pathogen.
D. The plasma cell traps secreted antibody molecules in its extracellular matrix and
uses these antibodies to bind to the pathogen.
E. The naive B cell expresses a membrane-bound form of the antibody as a receptor, and secretes that same antibody when it differentiates into a plasma cell.

Answer 1

A naive B cell expresses a single specificity of antigen receptor and differentiates into a plasma cell that secretes antibodies with the same specificity, ensuring targeted immune response to pathogens.

Step-by-step explanation:

The mechanism by which the adaptive immune response ensures that the specificity of the antibody secreted by plasma cells will recognize the same pathogen that initially stimulated the naive B cell antigen receptor and induced B cell proliferation is described in choice E.

A naive B cell expresses a membrane-bound form of the antibody as a receptor, and when it differentiates into a plasma cell, it secretes that same specificity of antibody.

This process begins when a B cell's unique B cell receptor (BCR) binds to an antigen. This antigen binding leads to the cell's activation, followed by clonal expansion, producing many identical B cells that secrete antibodies with an identical antigen recognition pattern to the original BCR.

This achieves specificity as the secreted antibodies will target the same antigens as those recognized by the initial membrane-bound receptors.