B lymphocytes help defend the body by recognizing antigens and, after activation, developing into antibody-secreting cells. This lesson explains how B cells recognize antigens, how the immune system limits responses against the body's own tissues, and how B cells are activated.
A B cell carries surface immunoglobulin, also called a B-cell receptor (BCR). Unlike T cells, B cells can recognize native, unprocessed antigen directly. They do not require an antigen-presenting cell or an MHC molecule simply to bind their target.
All flashcards
What can a B-cell receptor recognize directly?
It can bind native, unprocessed antigen without an antigen-presenting cell or MHC molecule.
How do clonal deletion and clonal anergy differ?
Deletion removes a self-reactive B cell, usually through apoptosis; anergy makes it functionally unresponsive without removing it.
What are the main outcomes of activated B-cell differentiation?
Activated B cells can become antibody-secreting plasma cells or memory B cells that support later responses.
What is the basic structure of an antibody?
An antibody has two identical heavy chains and two identical light chains, forming two antigen-binding sites and an Fc region.
What changes during antibody class switching?
The antibody class and its associated functions change, but its antigen-binding specificity remains the same.
Quiz questions
How does a B cell receive helper T-cell signals when responding to many protein antigens?Answer: It presents processed antigen fragments on class II MHC to a Th2 cell, which supplies cytokines.
Which description best fits secreted IgM?Answer: It commonly appears early in a primary response and forms a pentamer that can activate complement.
Which antibody class is associated with mast cells and allergic responses?Answer: IgE, which binds strongly to IgE-specific Fc receptors on mast cells.
What is a typical feature of passive immunity?Answer: Transferred antibodies can provide rapid but temporary protection without creating the recipient's immune memory.
What can memory B cells contribute to when the same antigen is encountered again?Answer: A faster and larger secondary antibody response.
Based on Anatomy and Physiology 2e by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.