Question

After activation with a thymus-dependent antigen, B cells migrating directly from a primary focus to the medullary cords in a lymph node will differentiate into plasma cells that secrete predominantly ____ antibodies.

a. IgG
b. IgA
c. IgM
d. IgE
e. IgD

Answer 1

Activated B cells differentiate into plasma cells that predominantly secrete IgM antibodies as a first response to a thymus-dependent antigen before other antibody classes, like IgG, are produced in larger quantities upon reexposure.

Step-by-step explanation:

Activation and Differentiation of B Cells

When B cells are activated by a thymus-dependent antigen, they undergo clonal expansion and differentiation. The activated B cells then migrate to the medullary cords in a lymph node, differentiating into plasma cells. Plasma cells are the immune system's antibody factories, dedicated to the production and secretion of antibodies. The IgM antibodies are the first type to be secreted by newly differentiated plasma cells. IgM is often secreted as a pentamer, allowing it to bind more avidly to antigens, although it is generally less stable in binding compared to IgG. IgG antibodies are typically secreted in large amounts upon subsequent exposure to the same pathogen, offering stronger and more sustained protection.

After activation with a thymus-dependent antigen, B cells migrating directly from a primary focus to the medullary cords in a lymph node will differentiate into plasma cells that secrete predominantly IgM antibodies. This is because IgM is usually the first class of antibodies produced during the primary response to an antigen.

Answer 2

Activated B cells differentiate into plasma cells that initially secrete IgM antibodies, which are the predominant type produced in the early stage of an adaptive immune response. C is the correct option.

Step-by-step explanation:

After activation with a thymus-dependent antigen, B cells migrating directly from a primary focus to the medullary cords in a lymph node will differentiate into plasma cells that secrete predominantly IgM antibodies.

This is the initial antibody class secreted upon an adaptive immune response.

Plasma cells derived from activated B cells initially produce IgM, which can bind to antigens but not as stably as IgG, which usually appears later upon reexposure to the same pathogen.