14). Clonal selection and differentiation of B cells activated by antigen exposure leads to the production of ________. A) large
quantities of the antigen initially recognized B) vast numbers of B cells with random antigen-recognition receptors C) long-lived erythrocytes that can later secrete antibodies for the antigen D) short-lived plasma cells that secrete antibodies for the antigen
The correct answer is D) short-lived plasma cells that secrete antibodies for the antigen
Explanation:
Each B lymphocyte has an antigen receptor (BCR: B cell receptor), a surface immunoglobulin (IgM or IgD), that binds to specific domains of the antigen called antigenic determinants or epitopes. Only B lymphocytes with a high antibody affinity for the antigen, and which are capable of processing and presenting it, will be positively selected. In this contact between the two cells, an exchange of chemical signals takes place that leads to the activation, clonal proliferation and differentiation of B cells into two sister subclones: one of antibody-secreting plasma cells, and the other of memory primed B cells. Therefore, only these last positively selected B lymphocytes will survive, proliferate and differentiate into plasma cells, synthesizing and secreting antibodies of a single isotypic class, with a unique specificity and high affinity, improving the ability to adhere to the antigen and, thus , neutralize and destroy pathogens.
Otters are from keystone species from the subfamily of Lutrinae. Lutrinae is a branch of Weasel. The actions of the humans that can ensure that the sea otter will continue their function in the environment would be to establish in the Atlantic ocean a sea otter wildlife refuge and also pass laws to regulate the hunting of such species.
